Acoustic windscreen
A soundproofing measure, as used by Toyota and Lexus that differs from conventional laminated windscreens in that it has a special layer of transparent sound-absorbing material between two layers of glass.

Active Steering
A BMW option that works with the electric power steering to adjust the steering ratio (the number of turns lock-to-lock) and level of assistance, according to speed and driving style.

Bluetooth
A wireless electronic radio system allowing communication between phones, computers, digital cameras and so on. In some Bluetooth-kitted cars you can operate your phone and MP3 player through the car's controls and screens, for hands-free operation.

Boxer engine
A horizontally opposed engine, usually a flat four or flat six. The cylinders sit in two banks either side of a crankshaft, running parallel to the ground. Gives compact dimensions and a low centre of gravity, and is well suited to air-cooled systems. Modern boxer engines include Porsche's flat six (Cayman, Boxster) and Subaru's flat four (Impreza, Legacy) but other notable powertrains in this format include the Volkswagen Beetle's original flat four, the Citroen 2CV's flat twin and the Alfa Romeo flat four in the Alfasud. A popular format for engines for BMW motorbikes and light aircraft, too.

Brake assist
Part of most ABS systems these days, brake assist works to back up and even out your brake pressure in the event of an emergency stop; left to our own devices, most of us will lift off the brake pedal too soon.

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Cambiocorsa
Translates as 'race change': the F1-inspired sequential-shift gearbox option, with steering wheel-mounted paddleshifts, in Maseratis.

Camshaft
A shaft that rotates inside the engine, carrying cams that push the cylinder head valves open and closed co-ordinated with the up-and-down movement of the pistons. If it breaks, so does the engine.

Captain's chair
Often found in MPVs, this is a self-contained adjustable unit with integrated seatbelts, headrests, armrests and so on, and perhaps even its own air conditioning controls, DVD screen, audio controls...

Carbon dioxide (CO2)
Carbon dioxide is a waste product of the breathing process - for cars as well as living organisms. It's a greenhouse gas and a contributor to global warming. A car's carbon dioxide output is the criterion by which road tax is charged - the less it emits, the less annual road tax or, if applicable, company car tax, you'll pay. Measured in g/km - grams per kilometre.

Carbon fibre
A composite manufactured material, containing strands of pure carbon. It's light, strong and very expensive, which is why it's reserved mostly for racing cars, supercars and low-volume sports cars.

Catalytic converter
A little gadget in your exhaust system that converts harmful emissions into more friendly by-products, such as nitrogen, water and carbon dioxide. Compulsory-fit in all petrol-engined cars sold in the EU since the 90s, it is also described as an exhaust catalyst.

Chassis
The automotive equivalent of a human skeleton, the chassis is the basic frame that supports the car's body, engine, suspension and other moving parts.

Child seat
A removable chair designed to protect babies and small children - and a life-saving device. A child seat will stop your child being flung forwards through the windscreen or against a car's hard surface in the event of a crash. There are special fixing points in most modern cars, which make a seat more secure than those simply hooked through the seatbelts. Even small teenagers should sit on some kind of booster seat, which lifts them up so that their seatbelts restrain them correctly and ensure that they do not slide under the belt. [See also: Isofix]

Chipping
Tuning or modifying an engine by reprogramming its electronic engine management system. A useful and effective way of liberating more power, unfortunately it also usually invalidates a manufacturer's original engine warranty (although independent tuners should offer their own guarantee). However, long-term reliability from a 'chipped' engine may be dubious - if it was possible to get that much power out of the engine safely, engineers would probably have designed it that way in the first place.

CNG (compressed natural gas)
At one time proposed as an eco-friendly alternative fuel, it never really took off in the UK. Clean-burning, it can be obtained from a domestic supply and used in a petrol engine with very few modifications. Volvo marketed bi-fuel CNG-compatible models which could also run on petrol, but few came to the UK.

Coachbuilders
In the early days of the car industry, car companies delivered rolling chassis with engines to external coachbuilders - most of which started out making horsedrawn carriages - for finishing off with body panels, seats and interior trim. Once all-in-one construction became the norm, just a few such firms survived doing specialist conversion work such as hearse building, but they're making a comeback now, building bespoke vehicles for the world's super-wealthy.

Collision-Mitigating Brake System
This Honda technology, used in the new Legend, is an automatic braking function that works with the active cruise control to apply the brakes hard - and pre-tension the seatbelts - if it senses an imminent impact.

COMAND
Mercedes-Benz's control system for phone, sat nav, audio and other non-essential in-car functions, all in one unit. Simpler than BMW's iDrive and Audi's MMI.

Common-rail injection
Direct injection technology; fuel injectors are sited to squirt fuel directly into the cylinder, instead of into a chamber to be pre-mixed with air. Fuel is pumped to the injectors at very high pressure from a central accumulator rail, hence the name.

Composite panels
A generic term that can refer to carbon fibre, fibreglass or plastic panels, but usually means some kind of reinforced plastic. Lightweight, and now cheap to produce, plastic composites are increasingly used in combination with a spaceframe construction to make low-volume sports cars.

Concept car
Designed to attract media attention and feedback from potential customers at motor shows, they preview new styling directions, new features and manufacturers' intentions - or simply allow a design team to get imaginative. Many never make production, or look far more conventional when they do - although occasionally a concept is little changed from the real thing, as in the case of the Audi TT.

Contract hire
Instead of buying a vehicle outright, customers can lease one over a period of one to four years. Then it's simply handed back to the lease company, though some deals will give you the option to buy it. Usually used for company car purchases. [See also:
APR, Lease, PCP]

Crossover
A car that combines the attributes of models from two or more different segments - such as a car-like 4x4-cum-hatchback/estate, halfway between a conventional low-riding car and an all-out SUV, with implied sportiness.

Cruise control
A device that keeps the car at a selected speed, until you brake or accelerate; set or deactivated via a button or lever on the steering wheel. Popular with high-mileage execs on the motorway - just make sure you don't nod off at the wheel with your car still cruising on. [See also: Adaptive cruise control]

Crumple zone
A section of the car, fore and aft of the main passenger area, designed to absorb most of the energy during a collision by crumpling. Draws the force of the impact away from the car's occupant.

Coupe-cabriolet
A convertible with an electrically powered metal folding roof instead of a soft canvas hood. The roof will fold and slide in sections, stowing away behind the seats or into the boot for open-top driving, but offers better warmth, security and overall refinement when the weather's bad or when it's parked up. The problem is, such roofs are heavy, take up a lot of space at the rear end and can lead to awkward back-end design.

CVT (continuously variable transmission)
A gearless automatic that uses an elastic drive band to continuously vary the ratio between engine and wheel speed, ensuring that it stays permanently in the correct powerband. You accelerate, the wheels are turned faster, with no steps or ratios (although these can be artificially engineered-in). First seen in cars from Dutch manufacturer DAF, it's a weird but simple system, usually applied in small-engined cars: however, in recent years manufacturers have worked out how to use such as system in larger, more powerful vehicles - Audi's Multitronic gearbox is a CVT, for example.

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Dampers
The suspension component that works with the shock absorbers to stop the car bouncing up and down on its springs. Traditionally hydraulic (using fluid reservoirs) but increasingly uses electronic systems. Adaptive or active dampers act to vary their force according to driving style; they reduce spring rate still further under sporty driving but allow more give when cruising

Diesel
Formerly the preserve of commercial vehicles, diesel (sometimes referred to as derv) is now the fuel of choice for a large proportion of cars of all sizes, but especially large family cars, MPVs and 4x4s. Diesel fuel contains more energy, litre for litre, than petrol and so diesel engines give more miles to the gallon. They also produce less carbon dioxide, meaning lower taxation. Traditionally diesels have produced more harmful emissions of particulates (unburnt soot) but modern fuel injection systems and now, in some vehicles, particulate filters, have helped reduce this. Diesel ultimately has the potential to be very green, as diesel fuel can be made from sustainable organic plant sources (biodiesel) as well as fossil oils.

Differential
Splits engine torque (pulling power) between the wheels to stop the outside one spinning when accelerating in corners. Also used to divide torque between the front and rear axles in four-wheel drive vehicles. Locking differentials can help overcome particularly tricky traction problems.

Direct injection
A fuel injection technology that involves injecting fuel directly into the cylinders to be mixed with incoming air, rather than the air being mixed with the fuel in a chamber prior to cylinder entry. The high-pressure fuel injectors are sited along a rail shared by several cylinders. More efficient, as a higher compression ratio can be set, with more precise control over combustion; emissions are also lowered, especially when the engine is cold.

Disc brakes
Discs attached to the wheel hubs are gripped by a pair of callipers with pads either side, slowing or stopping wheel rotation. Standard on most cars, at least on the front wheels.

Displacement on Demand
A GM system, also known as Active Fuel Management, that shuts down some of a large engine's cylinders - usually three out of six, or four out of eight - when the car is cruising, to save fuel. When the driver asks for acceleration the valves automatically open to give full engine capacity. Said to reduce fuel consumption in large cars by up to 10%.

Downforce
Downward pressure exerted by the flow of air over and under the car's body. Big wings and front spoilers create a lot of it, thereby increasing high-speed stability and grip. [See also: Aerodynamics]

Drifting
Deliberately inducing oversteer to make forward progress at a sideways angle. Useful in motorsport to get a car round a corner quickly, but has now developed into a sport in its own right, with drivers judged on style, speed and general flashiness.
Video: How to Drift

Drivetrain
Refers to every part involved in the transfer of power to the wheels, namely the engine, clutch, gearbox, differential and driveshafts. Often used interchangeably with powertrain, although that term is sometimes intended to refer to just the engine and gearbox.

Drive-by-wire
See Throttle-by-wire.

DRLs (daytime running lights)
Headlights that stay on all the time. Once standard-fit in all Volvos and Saabs sold in the UK, as they're compulsory in Scandinavia. Plenty of evidence to suggest that they reduce accident rates, particularly on gloomy, grey days, so the EU is considering making them mandatory.

DSG
Direct Shift Gearbox, in Volkswagen-Audi language. A sporty semi-automatic gearbox with automatic double-clutch system and sequential-shift gearchanges as well as a fully auto mode using a torque converter. Audi has now started referring to it as S-Tronic, leaving the DSG label for other parts of the VW Group.

DVLA
The Driver and Vehicle Licensing Agency, where you register changes of vehicle ownership. Sometimes referred to (by Arthur Daley types) as 'Swansea' after the location of its HQ. If 'the documents are in Swansea' don't put any money down until you've seen them.

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EBD (electronic brakeforce distribution)
A component of modern ABS systems. Evens out brake pressure and spreads it between the wheels, improving your chances of avoiding a skid.

ECU (electronic control unit)
The electronic brain or black box that keeps the engine running smoothly, by monitoring its behaviour and controlling factors such as air/fuel flow and ignition timing.

Electronic parking brake
A button, usually in the centre console, which activates the parking brake electronically, rather than a handle that uses hydraulics. Some systems also release automatically when you hit the throttle.

ESP (electronic stability control)
An electronic system, usually integrated into the ABS, which monitors yaw (the angle and direction in which the vehicle is travelling) and the steering wheel angle to assess stability. If it detects that the car is skidding or becoming unstable, it then cuts the throttle or applies braking pressure to individual wheels to re-establish control. ESP is particularly important in vehicles with a high centre of gravity, such as 4x4s, and there are calls to make it compulsory-fit. [See also: Traction control]

Ethanol, E85
Ethanol is touted by some as a fuel of the future. It's a biofuel synthesised from organic sources, thus cancelling out carbon dioxide emissions, cutting down on fossil-fuel use and dependency on Middle Eastern oil (hence the US interest). Can be used in petrol engines with little modification. E85 is a blend of 85% ethanol and 15% gasoline that demands even fewer mods.

EuroNCAP
The European New Car Assessment Programme. An independent scheme that assesses the safety of every new car by carrying out simulated crashes in a laboratory. Ratings range from one to five stars, with five stars for overall crash protection the best result. Separate ratings out of four stars for child protection (using a manufacturer-supplied child seat) and pedestrian protection have also been introduced.

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Fibreglass, glassfibre
A resin and glass composite that's relatively light and cheap to produce, hence its extensive use for body panels for kit cars. It's also easy to break. Responsible for the survival of classic cars such as the Reliant Scimitar, as it doesn't rust.

FFV, FlexFuel
FFV is Ford's term for its E85-compatible engines which can also run on conventional gasoline. The Focus FFV is one of the few ethanol-fuelled cars on sale in the UK as yet, along with the Saab Biopower models. GM's term, FlexFuel, denotes a car which can use E85 or petrol; not to be confused with dual-fuel or bi-fuel, terms used by various manufacturers for LPG- or CNG-petrol models.

Four-wheel drive
In a four-wheel-drive (or all-wheel-drive) vehicle, power is supplied to both the front and rear axles, though not necessarily all the time. Some systems have full-time four-wheel drive, with power sent in a fixed ratio to both front and rear pairs of wheels: others have a part-time or 'torque on demand' system, where power goes to one axle unless a loss of grip is detected, with power then automatically sent to the axle with the most traction. Many high-performance cars with four-wheel drive have sophisticated systems that can automatically vary the power sent to the wheels, according to which wheel has the most grip on the road. Some 4x4s are front- or rear-wheel drive for normal road use, but the driver can select four-wheel drive to go off-road.

FSI
A Volkswagen-Audi term: fuel stratified-charge injection. A direct-injection petrol system with an extra stratified-charge mode: when the engine is not working hard, fuel is injected later in the combustion cycle and swirled into the cylinder to create a charge at the point of ignition. Allows for a very lean fuel-air mixture, and thus improved economy. TFSI denotes a turbocharged engine with this technology.

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G-force
The measurement of lateral acceleration, or how hard a car pins you to your seat when cornering or gaining speed. One g is equal to the force of gravity.

Grand tourer, GT
Refers to a sports car, usually a four-seat coupe, where the emphasis is on comfort and luxury rather than on-the-edge handling. Think Mercedes-Benz CL, Maserati Quattroporte, etc.

Grey import
A 'grey import' is a car that has been shipped into the country for sale without the manufacturer's blessing. Most of these in the UK are Japanese models, often high-performance sports cars or useful 4x4s and MPVs. Grey imports are different to parallel imports, which are cars sourced from abroad but which are technically the same as the model offered here.

Gross vehicle weight
The weight of a car when it has a fully loaded boot, its fuel tank topped up and its maximum number of passengers on board. The gross vehicle weight is a useful figure to know if you're calculating how much your car can tow, for example.

Gullwing doors
Doors which hinge at the top rather than the front or back. Much used in concept cars, as they look spectacular in photographs, and as they open wide for a good view of the cabin. A crucial component in supercar fantasies, too.

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Head-up display
As used in fighter planes. A device which projects information such as speed, engine revs and even directions from the sat nav on to the windscreen, where the driver can read it without taking his eyes off the road

Heel-and-toe
The action of blipping the throttle pedal with your heel when braking and shifting down through the gears at the same time. The only way to be quick on a track, as it enables the driver to get instantly back on the power as soon as the braking for a corner is done.

Hemi
High-performance Chrysler/Dodge engines with hemispherical combustion chambers that give a good swirl of fuel-air mixture for efficient combustion and protection against heat losses. The technology dates back to the 30s and was tested in V12 tank engines as well as aeroplanes, before being fitted in a road car in 1951.

Hill Descent Control
An electronic aid for 4x4s; works with the ABS to stop the vehicle running away on a steep slope, automatically applying the brakes if necessary. In its latest Land Rover iteration, the pre-set top speed downhill can be altered via the cruise control function.

Hill Start Assist
An electronic aid that automatically applies braking pressure when pulling away on a hill until the throttle is pressed down far enough, to prevent you from slipping backwards.

Hofmeister kink
Named after BMW's director of design in the early 60s, Wilhelm Hofmeister, and now a key feature of BMW's design identity. It's the curve or bend in a car's C-pillar (the bit between the rear window and the rear windscreen). The first BMW to have this was the 1961 1500, although it's not a design touch exclusive to the company.

Homologation
Qualifying a car to race or rally in a series meant for cars based on production models by making road-going counterparts - usually high-end, low-volume versions such as Porsche 911 GT3 RS, Skoda Fabia vRS and Subaru Impreza WRX STi. Incidentally, Ferrari's GTO stands for 'gran turismo omologato', Italian for 'grand touring homologation'.

H-point
An interior designer's term, this refers to the average hip-level entry point of people climbing into the cabin. A car with a higher H-point will be easier to get into and out from, as opposed to one where you sink down into the seat and then have to haul yourself upwards to get out. An increasingly important consideration for designers, with an ageing population to cater for, it also indicates how easy it will be to load child seats and small children.

Hybrid powertrain
An engine working in partnership with one or more electric motors, such as in the Toyota Prius. The motor(s), running on battery-supplied power, can simply give extra boost (called a mild hybrid) or can take over and allow for the engine to shut down completely at low speeds or in stop-start city traffic (a full hybrid). Either way, overall fuel economy is improved in most driving conditions. The batteries don't need to be plugged in to recharge either, as they cleverly recapture all the energy usually lost when a car brakes. So far, hybrids have combined motors with a petrol engine, but ultimately, diesel-electric hybrids promise the best economy.

Hydraulics
Fluid, generally oil, is forced through a small cylinder to create pressure. Used in brakes, clutches and power steering systems - or, in the case of some Citroen models, the suspension system.

Hydrogen fuel cell
A fuel cell that uses hydrogen as a fuel source: taking in oxygen to create a chemical reaction that produces energy, its only by-product is water. The energy is stored in a battery as electricity to power a motor. Hydrogen is widely seen as the fuel of the future, although its production is not necessarily pollution-free. [See also: ZEV]

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iDrive
BMW's control system for non-core functions such as hi-fi, sat nav, ventilation/air conditioning, seat position and phone, using scroll-down menus, a large dial and buttons all in one computer-style unit. Similar in concept to Audi's MMI and Mercedes' COMAND, but has become a byword for overcomplexity

Ignition
The system that creates and controls the timing of electrical sparks which ignite the air/fuel mixture in the engine.

Independent suspension
Each wheel is sprung separately, so if one hits a bump it doesn't affect the others. A system used in most modern road-going passenger cars, especially at the front. Makes for a smoother ride and better handling. See also Live axle.

ISG (integrated starter-generator)
A combination of the ignition and alternator into a single unit. More efficient and reliable, it allows for a system further combined with, for example, Stop-Start and regenerative braking technologies for fuel-saving. Can drive a small electric motor, as in so-called mild hybrids, to supplement the engine power.

Isofix
A standardised system of fixing points to anchor child seats into a car. Now standard in most family cars and other models, it enables the safe use of compatible child seats. [See also: Child seat]

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JTS, JTD
Alfa/Fiat terms to indicate direct injection of fuel into the cylinders. JTS is the petrol version, JTD the diesel.

Judder
A low-frequency vibration of the car's clutch or brakes, often an indication of imminent mechanical problems - although sometimes just poor engineering or clumsy driving. Feels like a washing machine on a spin cycle.

Jump-start
A process whereby a car with a flat battery is started using jump leads connected to the battery of another car with its engine running.

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Kerb weight
The weight of a vehicle that's ready to drive, with its fuel tank 90% full and a 68kg driver and 7kg of luggage on board. Like gross vehicle weight, it's a useful indicator for calculating how heavy a trailer you can tow.

Key fob
Getting bigger and clumsier, many now contain remote central locking transmitters, torches, and electronic chips for keyless entry and security devices.

Kit car
A car assembled from a collection of parts sold in kit form, usually with engines and drivetrains from old donor cars (often Fords or other mass-market models easily found in scrapyards). If you're handy with a spanner, it's a cheap way of being able to own a sports car. You can get kits to create lookalike Ferraris, AC Cobras, Lamborghinis... although some are more convincing than others. Some kit car makers now also offer turn-key cars (ready-built kit cars).

KPH
Kilometres per hour - measurement of speed used in the metric parts of the world.

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Ladder-frame chassis
This construction method - for old-school 4x4s, pick-up trucks and vans - is rugged for off-roading and load-hauling, but not ideal for refinement and ride comfort. It's also referred to as body-on-frame, referring to a separate chassis with attached passenger cell rather than a monocoque or unibody construction

Lease
Like hiring a car on holiday, only for a period of years rather than days. Appeals to those who can't afford a new car, but want to be seen in one. You don't actually get to own the car yourself. See also APR, Contract hire, PCP. [See also: APR, Contract hire, PCP]

LED (light emitting diode)
LED lights are more efficient and last a lot longer than normal light bulbs. They also illuminate more quickly, which makes them particularly useful for brake lights, and can illuminate to different degrees in response to the firmness of the brake pressure. Also used in many car interiors now.

Lift-off oversteer
When a car's rear end slides sideways as a result of you lifting off the throttle mid-bend. It's often followed by a trip through the local scenery or spin-off into the gravel if you're lucky, a trip to hospital if not. An experience known to many over-enthusiastic Peugeot 205 GTi owners. [See also: Oversteer]

LSD (limited-slip differential)
A type of differential that allows each wheel to rotate at different speeds within a pre-set parameter. Cuts down on wheelspin in slippery conditions. Traditionally a mechanical torque-sensing (Torsen) system that works on the different torque inputs to each shaft, although new electronic, speed-sensitive, viscous-pump set-ups are becoming more common. Electronic LSD systems work in parallel with ABS to apply braking pressure to a wheel spinning too fast.

Live rear axle
A single, heavy suspension bar that connects the two rear wheels. Often contains drive components such as the differential. Usually used in hardcore off-roaders and pick-up trucks as it's tough and simple. Cheaper than independent suspension to make, but not as good for either ride or handling.

LPG (liquefied petroleum gas)
Bi-fuel or dual-fuel LPG-petrol cars were popular for a while thanks to large tax breaks, exemption from London congestion charge and grants for converting an engine. Although said to burn more cleanly than petrol, this is now disputed, plus the cost of conversion now outweighs the benefits in most cases. Some owners of ultra-thirsty 4x4s, trucks and American cars still swear by it, but pumps are getting more difficult to find.

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MacPherson strut
An independent suspension system with combined springs and dampers, commonly believed to provide the best ride and handling balance. [See also: Independent suspension]

Magnetic ride control
As in the current Chevy Corvette and top-end Cadillacs. A multi-mode adaptive damping suspension system that uses dampers with a fluid containing magnetic particles. When the fluid is energised by a charge - triggered by sensors monitoring driving style - the particles align to firm up the dampers. Helps cut body roll and wallowing in large SUVs in particular. Also known as rheostatically charged suspension.

Mid-engined
Cars with their engines mounted behind the cabin but in front of the rear wheels such as the Lotus Elise, Ferrari F430 or Honda NSX. Most supercars adopt this approach, as it achieves an ideal front-to-rear weight balance and allows for very low mounting of the engine, which thus lowers the car's centre of gravity and aids handling.

MMI
Audi's Multi-Media Interface: an all-in-one control for non-core functions such as hi-fi, sat nav and air conditioning, using scroll-down menus, a large central dial and buttons mounted between the front seats. Similar in concept to BMW's iDrive and Mercedes-Benz's COMAND, but a little more user-friendly.

Monocoque construction
Also known as unibody; the usual construction method for roadgoing cars, with an all-in-one chassis/passenger cell structure to which suspension, powertrain etc are attached. First seen in racing cars, it has now largely superceded traditional ladder-frame build even in many 4x4s.

MoT
Standing for Ministry of Transport, this refers to the annual test all cars over three years old have to go through each year in the UK. Registered test centres will examine your car's brakes, lights, tyres and other safety-related items before issuing (or refusing) a certificate. It also measures a car's exhaust emissions. This is legally required and you can't get a new tax disc without a valid MoT. A new MoT won't necessarily indicate that a car is reliable, but it should show that it's basically safe.

MPG (miles per gallon)
The figure generally quoted is for combined fuel consumption, a figure calculated from a mixture of city and open-road conditions; manufacturers usually quote urban and extra-urban figures, too. You'll be lucky to match these figures in real life, though: they are obtained in ideal simulated conditions on a test track, by experienced test drivers. Their benefit is in allowing you to compare similar models, knowing they've been through the same tests. Mainland Europeans now use litres per 100km instead.

MPV
Multi-purpose vehicle, or people-carrier; known in the US as a minivan. These are usually large family vehicles with an emphasis on interior space and versatile seating layouts; many seat six, seven or eight people. MPVs have evolved over the years from basically being vans with seats to sophisticated, comfortable, well-equipped and fashionable status symbols. Popular MPVs include the Renault Espace and Ford Galaxy; similar principles have also been applied to create new classes of smaller compact MPVs such as the Renault Scenic and Citroen Xsara Picasso, and even mini-MPVs such as the Vauxhall Meriva and Fiat Idea.

Multi-link suspension
Rear suspension layout in which a series of arms replace the damper. They keep the wheel as upright as possible, improving the ride.

Multiplex wiring
System of electrical distribution within a car, using a single network that's able to support functions such as automatic headlights, rain-sensing wipers and lights, as well as sat nav and display screens.

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Neck-Pro
Mercedes-Benz's anti-whiplash active head restraints. Linked to sensors which monitor the likelihood of an impact from behind; if you're about to be rear-ended, they move forwards and upwards for optimum protection of the head and neck.

Night Vision
Formerly military-issue kit, now offered in certain ultra-luxurious road cars. Uses a thermal imaging camera (infra-red) to detect pedestrians, animals or other heat-emitting objects, and then projects images of these onto an in-dash screen.

Naturally aspirated
Used to describe engines that produce their power without the assistance of a supercharger or turbocharger, which take in their air naturally.

Nurburgring
The Ring. Mecca for road-racers and petrolheads, this legendary 13-mile race track in Germany is said to be the most demanding in the world. In its many incarnations it has hosted grands prix, 24-hour endurance races and many other events since the 20s. The Nordschlieffe circuit circles the Nurburg castle; this is much-used for testing of prototype cars, and is an open public road (one-way, with a toll) for much of the year.

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Octane
The octane rating of a fuel tells you how much the fuel can be compressed before it ignites, strictly due to compression. In a high-performance, high-compression engine, if the fuel ignites too soon - before the spark plug fires - this could result in engine 'knocking'. Thus high-performance cars usually need a high-octane fuel, such as super-unleaded petrol with a rating of at least 98 octane, expressed as 98 RON. UK petrol pumps dispense fuel from 95 to 102 RON.

Overhang
The part of the car's body that protrudes further than the front or rear wheels. A car can have long overhangs but still not be very roomy for passengers - all the space is under the bonnet or in the boot - or have short overhangs and very little boot space, like many MPVs.

Oversteer
When the rear end of the car loses grip and it rotates in the direction of the steering, usually as a result of braking on bends or simply applying too much throttle. It often results in facing the wrong way up a road or a trip through a hedge, though it's part and parcel of racing on a track. Hooligans do it for fun. Easier to achieve in a rear-wheel-drive car, whether you want to or not. [See also: Lift-off oversteer, understeer]

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Paddleshift
A pair of paddle-type switches mounted on or behind the steering wheel of some cars with automatic gearboxes, enabling easy manual-style gearchanges. Usually you push or pull one to shift up a ratio, the other to go down one when in sequential-shift mode.

Panoramic roof
A large glass roof panel, usually fixed into position rather than a sliding/opening sunroof. Should be specified in combination with sunblinds, to stop your car turning into a greenhouse. (Although, strictly speaking, you can't actually have a panoramic roof because it's above you, not around you.)

Parking sensors
Most systems use radar sensors mounted on the car's bumpers and give a warning beep if you get too close to another car; some also integrate a rear-view camera and in-dash display screen. Also known as PDC (Park Distance Control).

Particulate filter
Traps nasty particles of unburnt hydrocarbons, the soot associated with less clean diesel engines; a maintenance-free device intended to last the life of the engine. A very effective and cheap anti-pollution measure.

PCP (Personal Contract Purchase)
A form of lease where the driver signs up to hire a new car for a set period, with an agreed capped mileage, but has the option of buying it at the end. [See also: APR, Contract hire, Lease]

PASM (Porsche Active Suspension Management)
Two modes, normal and sporting, the latter lowering the 911, for instance, by 10mm and firming up the dampers. Capable of monitoring driving dynamics and adjusting damping accordingly.

Personal/private plate
A number plate with a special configuration of letters and numbers usually designed to mimic the car or driver's name (eg K4 REN). These are typically used to disguise the age of the car, or express one's 'personality'. New personal plates can be chosen and bought straight from the DVLA to fit on a brand new vehicle.

Piezo injection
A type of direct injection where solenoid controls are replaced by ceramic injectors which expand and contract under an electric charge. In a petrol engine, these are situated between the valves and the spark plugs. It's also known as jet-guided injection, since the fuel/air mixture ignites right by the injection jet rather than swirling in the combustion chamber. Allows for a lean fuel-air mix throughout the rev range, thus saving petrol, and up to four fuel injections per engine cycle, but needs sulphur-free fuel. Also applied to diesel engines. Makes for ultra-precise fuel injection at even higher pressures than solenoid systems.

Platform
The basic structure of the car, or its essential underpinnings. One platform is often used to form the basis of many closely related models for different brands - eg the Volkswagen Golf/Audi A3/Seat Leon - or the creation of different body styles around the same structure (Renault Megane, Scenic, Megane CC).

Plug-in hybrid
The problem with current hybrids is that they have a limited range in electric-only mode, so aftermarket firms have developed external charging systems to boost the battery power - just plug it into a mains socket. Factory-fit plug-ins are on the way as an option with production hybrids such as the Prius.

Power band
The sweet spot in the engine's rev range where it delivers the bulk of its power. Diesel engines typically develop their peak power quite low down the rev range and performance-orientated petrol engines high up; Honda, for example, is renowned for a very high-rev powerband from its sports car engines fitted with VTEC variable valve timing. [See also: Bhp, torque]

Power steering
Traditionally uses a chamber of hydraulic fluid pumped around to back up the force applied by the driver to the steering wheel, but most new cars now have an sensor-driven, electronically controlled system, sometimes known as EPS (electric power steering). EPS entails pre-programming of characteristics such as steering feel.

Pre-Safe
A Mercedes-Benz system that tensions seatbelts, optimises seat positions, shuts windows and the sunroof and inflates seat bolsters to get you in the best position if the car's sensors reckon you're about to have an accident, and deploys airbags according to the predicted force of the impact.

Pre-tensioning seatbelts
Belts designed to take up the slack and grip the body more tightly when sensors anticipate a crash, thus limiting the distance you can be flung forwards or jerk backwards again.

Prototype
A fully functioning pre-production vehicle used by manufacturers to evaluate the design and performance of a forthcoming model. These are the cars our spy photographers catch out testing. Most get crushed after their testing life is over, though some important prototypes are kept by companies for their own archives and museums.

Pyrotechnic bonnet
A bonnet designed to reduce injuries to unfortunate pedestrians the car may collide with, as in the current Jaguar XK. Uses deployment device similar to an airbag to pop up the bonnet for absorption of the impact and to reduce risk of the person hitting the rigid engine.

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Q4 and Q2r
Q4, from 'quadrifoglio', is Alfa Romeo-speak for four-wheel drive. Alfa's full-time torque-split system has a central self-locking Torsen differential. Q2 is a self-locking front differential for front-wheel-drive models, using a Torsen LSD to distribute torque between the front wheels for optimum traction, grip and stability, reduced understeer and lesser intervention by the traction control and ESP.

Q-car
A wolf in sheep's clothing - a car that doesn't look very fast, but is. The name may have been derived from the Metropolitan Police term for a rapid unmarked car or 'quiet' car, but it now most often applies to German saloons with big engines, such as V8-powered BMWs with the badge-delete option.

Quattro
Audi's patented all-wheel-drive system, these days a full-time 4WD with central Torsen differential. Audi likes it written with a small Q. First came to prominence on the iconic Group B rally 'Ur-Quattro' coupe of the early 80s, now offered in all of the company's models.

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Rack-and-pinion steering
When the steering wheel is rotated, a gear on the end of the steering column moves a toothed rack left and right to change the angle of the front wheels. Favoured by sports car makers for better steering feel and used in most road cars these days - even by Mercedes, which clung onto the old recirculating ball system for many years.

Redline
The maximum number of revolutions the engine can make per second, indicated by a red section on the rev counter. In simple terms, racing cars tend to have high redlines, budget economy cars very low ones; the further away from the redline you stay, the less fuel you will consume and the less your engine risks wear and tear.

Regenerative braking
Capturing the energy that would otherwise be lost under deceleration and braking, storing it in batteries and then using to power ancillary systems such as air conditioning, electrical gadgets and non-essential functions. In a hybrid, this is how the batteries are recharged; will increasingly appear in non-hybrid cars to reduce fuel consumption and emissions.

Rev limiter
A device designed to limit an engine's rpm in order to protect it from damage. Not necessarily the same as the redline.

Residual value
The resale value of a used car. A car is said to have strong residuals if it holds its value well. Most cars lose value steeply in the first year they are on the road, with more heavy losses for the next couple of years. The strength of residuals varies between brands and type of vehicle: typically, the German manufacturers' cars enjoy strong residuals, but cars with large petrol engines lose their value the most quickly, especially saloons.

Rollover hoops, rollover bars
Often listed in spec sheets for convertibles, but we hope that you never get to see them. They spring up - usually from behind the seats - if sensors predict that you're about to turn turtle, so that they hit the ground before your head does. Not to be confused with anti-roll bars, which are stabilising bars across your car's suspension. Or roo bars, which Aussies fit to the front of their utes.

RPM (revolutions per minute)
The number of times the engine's crankshaft rotates in a single minute. The harder you press the throttle, the higher the rpm, depending on which gear you're in. The rpm rate is usually governed by a rev limiter so you can't push your car over the redline and blow its engine up.

Run-flat tyres
Tyres with a strengthened sidewall and structure that enable you to keep going after a puncture or blow-out without ruining your wheel. Usually fitted to free up boot space otherwise taken by a spare wheel.

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Sat nav
Satellite navigation. Uses a sophisticated locator device that gets a fix on the car's position, speed and direction of travel from satellites above the Earth. Linked to a CD or DVD of maps, the system can then direct you, road by road, to your desired destination. Simple sat nav systems can be bought from accessories shops as devices to stick onto your dashboard: more sophisticated systems use full 3D-effect colour mapping on a large display screen.

Scuttle shake
A familiar one for classic convertible drivers, this is where the dashboard shakes and rattles over a bumpy road, due to the loss of structural rigidity from having a canvas, rather than fixed steel, roof. Still an issue in some convertibles today, though the new coupe-cabriolets with metal folding roofs have overcome the problem.

Selespeed
Alfa Romeo's F1-style semi-automatic clutchless transmission option.

Semi-automatic transmission
A manual gearbox that changes gear automatically by replacing the clutch pedal with a system of electronic sensors and hydraulic mechanical actuators. You drive it through the gears as if you were in a manual, but do not need to push down a clutch pedal with your left foot.

Sequential-shift gearbox
As semi-automatic transmission, but with a simpler forwards-backwards gear lever motion to take you up and down the gears, rather than a manual-style H gate - invariably in combination with a fully automatic mode and usually with selectable 'sports' or 'comfort' modes determining gearchange time. Most sequential-shift transmission systems have steering wheel-mounted paddleshift-type buttons as well as the lever.

Service history
A documented history of a car's maintenance, this shows where and when each service has taken place. A manufacturer-supplied handbook, with stamps from main dealers, is the most desirable. You will need to show this if you have to make a claim on a car's warranty, to prove that it has been properly looked after, and when you sell your car, most buyers will expect to see it.

SH-AWD (Super Handling All-Wheel Drive)
Honda system similar to Ferrari's e-diff, but with four-wheel drive. Sends torque to the wheel where it's most useful - up to 100% to either rear wheel. Differs from other AWD systems in having an electromagnetic clutch at each rear half-shaft in place of a rear differential. If both rear wheels are slipping, torque goes up front. And instead of a centre differential, there's a device called a speed multiplier which allows front and rear axles to spin at different speeds. Maintains rear-biased handling, with super-quick reactions.

Side impact beams
Beams or bars of solid metal in the doors designed to stop them caving in and squashing the occupants in side-on collisions.

Skyhook
Maserati's name for its multi-mode adaptive damping suspension system.

SMG (Sequential Manual Gearbox)
BMW system based on a conventional manual gearbox but with the gearshift and clutch mechanisms operated by hydraulic actuators. Basically a semi-automatic gearbox; the fun of a manual without having to use your left foot - and with a full auto mode for lazy moments. Has steering wheel-mounted paddleshifts and a choice of sports settings ranging from smoothness to super-quick race-style shifts. There's a launch control mode in recent models, too.

Solenoid
A loop of wire that produces a magnetic field when an electrical current is passed through it. In a car, the starter solenoid receives a large electrical current from the battery and a small electrical current from the ignition switch. When the ignition switch is turned on (when the key is turned to start the car), the small electrical current tells the starter solenoid to relay the large electrical current to the starter motor.

Spaceframe construction
Usually aluminium these days, but steel in many classic racing cars. A body structure from tubular metal struts forms an integrated frame or 'cage' to which the body panels, suspension etc are then attached. Lightweight and strong, advances in production technology now make spaceframe construction more affordable and ideal for low-volume sports cars, specialist vehicles and racers.

Spec/specification
Sum-up of a car's equipment, gadgets, gizmos, refinements, accessories and so on. A car described as high spec these days should have air conditioning, nice seats, a CD player and sat nav; if it's low spec, you're winding the windows by lever and sitting on nasty nylon.

Spoiler
An aerodynamic device that diverts the flow of air in order to reduce drag or lift. Not strictly necessary in most road-going cars at legal road speeds, so in most cases it's a largely cosmetic device. Some high-performance cars have small spoilers that automatically rise up when a certain speed is reached. Often used interchangeably with 'wing', although strictly speaking a wing lets the air pass above and below. [See also: Aerodynamics, downforce]

Steering feel/feedback
Refers to the relationship between the amount cornering force (in 'g') being produced and the resistance felt through the steering wheel. Good steering feel gives the driver a good sense of how much grip is left and, therefore, more confidence in fast corners.

Steering ratio
The ratio of how far you have to turn the steering wheel to how far the wheels turn. A car with a low steering ratio means reaction to small wheel inputs, and thus a sporting steering feel; one which demands turn after turn of the wheel won't feel quite so obliging. Also measured in terms of the number of turns a car needs lock-to-lock; influential on turning circle.

Stop-Start
Turns the engine off when idling, such as when sitting in a traffic queue, and restarts it again when the brake is lifted or throttle pressed, cutting both fuel consumption and emissions. As seen in the early 90s in the Golf Eco, now making a comeback - on offer from Citroen and BMW but set to be used by many more manufacturers in the near future. In combination with integrated starter-generator (ISG) technology, can offer fuel savings near to those of hybrids without the extra weight and cost of a full hybrid powertrain.

Submarining
Describes how a car occupant can slide down and under their seatbelt in a crash, thus evading the restraint and losing protection from airbags. A particular danger for kids not in child seats, as adult seat belts are not designed to restrain them. Anti-submarining seats aim to reduce this risk, as do child booster seats.

Supercharger
A mechanically driven turbine that boosts engine power by forcing compressed air into the cylinders. As used in the first BMW-era Mini Cooper S and in many Mercedes models, where it is known as a Kompressor. Thought to give a smoother power delivery than a turbocharger.

SUV (Sports Utility Vehicle)
Loved by posh school-run mums (hence the nickname Chelsea tractor), wealthy footballers and farmers alike, the SUV is a tall, high-riding, four-wheel-drive vehicle designed to negotiate muddy terrain - though most rarely go further off-road than a supermarket car park. Now seen as politically incorrect due to high fuel consumption and arrogant road presence.

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Tachometer
More commonly referred to as a rev counter. Indicates the amount of revolutions per minute at which the engine is turning - and has a red section on its dial to tell you when you're revving too high. Not to be confused with a tachograph, which is what lorry drivers have in their cabins to tell them how many working hours they have left.

Targa top
A type of convertible with lift-out solid roof panels instead of a folding canvas hood or retracting hard-top. Usually leaves a central T-bar above the occupants.

Thatcham
Where car security systems are tested: the Motor Insurance Repair Research Centre, near Newbury. The centre rates and certifies security systems and is also involved in safety testing - it has recently been researching whiplash protection. It provides most of the data insurance companies use to set a car's insurance grouping.

Throttle-by-wire
An entirely electronic throttle control system in which there is no mechanical link between the driver's right foot and the engine.

Tiptronic transmission
A patented Porsche/Audi/Volkswagen automatic gearbox design that features a manual gear selection facility - known as a sequential shift - allowing you to shift up or down a ratio. Has subsequently been copied by other manufacturers.

Tonneau
Traditionally a canvas cover for the open section of a convertible, though usually now - in these days of full hoods and folding hard-tops - the cover (hard or fabric) over the hood/roof itself when it slides away.

Torque
The turning or twisting force imparted on the driveline by the engine, also known as pulling power, it indicates an engine's strength and flexibility (ie the ability to pull in each gear) rather than its power and overall speed. Normally measured in lb-ft or Newton metres (Nm). Big torque figures at low revs are a feature of large V8s, while high-revving four-cylinder engines normally have lower torque at higher revs. Diesels typically develop their maximum torque low down the rev range. [See also BHP.]

Torque converter
A fluid coupling used in automatic transmissions to transmit power from the engine to the wheels.

Torque steer
The tendency of a powerful front-wheel-drive car to pull to one side or become unstable during hard acceleration, due to excessive engine torque. Usually felt as a tug to the steering wheel. Common in turbocharged engines, though these days, usually curbed by traction and electronic stability control systems.

Torsional stiffness
Body rigidity. Aside from crash safety, indicates how much the structure is likely to flex and whether it'll get wobbly over bumps. A phrase usually used when describing convertibles and roadsters, as it determines whether they'll suffer from scuttle shake.

Track
The distance of the width between the centre of each of the front or rear wheels: the wider the track, the more stable the car should be.

Traction control
A device that detects wheelspin and cuts power or applies pulse braking to the offending wheel in order to regain grip, or traction. [See also: ESP]

TSI, Twincharger
Volkswagen term for an engine with both turbocharger and supercharger - how to extract large power outputs from small engines, in combination with FSI direct-injection technology. The supercharger boosts torque and power at the low end of the rev range, before the turbo takes over. Cuts out turbo lag, gives instant boost at all engine speeds.

Turbocharger
Forces compressed air into the engine with a turbine; like a supercharger, but driven by exhaust gases rather than the crankshaft. The delay common in early turbocharged cars between pressing the throttle hard and achieving acceleration is known as turbo lag. [See also: Supercharger]

Turning circle
The smallest circle in which a vehicle can turn 360 degrees with its steering on full lock. A tight turning circle means better manoeuvrability around town: the traditional black London taxi cabs are noted for their ultra-tight turning circles.

Twin Spark
As in Alfa Romeos; two spark plugs per cylinder. Used in early Alfa race cars, said to help extract more power from an engine without increasing emissions; gives more explosive and more thermodynamically efficient ignition, but it's costly and complex.

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Understeer
The tendency for a car to push straight on in corners instead of turning in the desired direction. Usually due to an excess amount of speed over grip/traction and more likely in a front-wheel drive vehicle. [See also: Oversteer]

Uniair
Fiat Group camless engine technology, to feature in upcoming Ferraris as well as Alfa, Lancia and Fiat models. Gives greater control over valve opening and closing, with hydraulic actuation of inlet and exhaust valves instead of a spinning mechanical camshaft, and each valve is independently controllable. Suitable for both petrol and diesel engines.

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V5
A car's British registration document, also known as the logbook. Don't buy a car without it.

Valvetronic
BMW engine technology for the cylinder head. The intake air charge is varied according to the valve openings, rather than from a throttle. Improves response times as well as efficiency.

Variable Valve Timing (VVT)
Valves control the flow of air/fuel mix into the engine's cylinders and the exit of the exhaust gas at the end of the combustion cycle. Variable valve timing indicates a sophisticated electronically controlled system that precisely adapts the amount each individual valve opens, and how long for, according to the driving style and demands from the throttle.

VDIM (Vehicle Dynamics Integrated Management)
A Lexus system that monitors and co-ordinates steering, suspension and braking to ensure optimum responses - in addition to helping to keep you out of a crash. Can automatically make steering and braking inputs according to situation. Less obtrusive than most traction control systems, which merely cut engine power, and has a positive impact on handling.

VIN number (Vehicle Identification Number)
A 17-digit alphanumeric code stamped on the vehicle, usually on the engine, which contains information about when and where it was built. Should tie up with the numbers quoted on the car's registration document (V5) and stamped elsewhere into the chassis.

Viscous coupling
A type of simple mechanical differential for four-wheel drive where torque is diverted from one axle to the other according to grip - as used in the Fiat Panda 4x4, though such systems are also used in high-performance sports cars like the Porsche 911 Carrera 4S and Lamborghini Murcielago.

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Wheelbase
The distance between the centre of the front and rear wheels, as viewed from the side. A car's wheelbase indicates how roomy its cabin is: a small car can have a long wheelbase yet be compact overall, if it has short overhangs. Often used to denote different-length variants of the same model: eg short-wheelbase and long-wheelbase versions of a car, the latter perhaps with an extra row of seats, or more limousine-like rear legroom.

Wind tunnel
An expensive aerodynamic research tool used to assess and improve airflow over a car's body. Anybody who's anybody in F1 has one and these days even the most humble superminis are wind-tunnel tested. Aerodynamics are not only important for stability and performance, but a crucial method of reducing a car's fuel consumption. The easier it slips through the air, the less fuel it needs to drink. [See also: Aerodynamics]

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Xenon headlamps
Electricity is used to ignite plasma gas inside the sealed headlamp casings, creating a bluish-toned light many times brighter than a normal bulb. Also known as gas-discharge lamps. Can be bought as aftermarket items, though quality and actual beam strength varies.

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Yaw
The angle of rotation (ie lean) that the car undergoes about its central vertical axis, indicating its stability. Yaw sensors are used in stability control (ESP) systems, as well as electronically controlled four-wheel drive systems.

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ZEV (zero emissions vehicle)
A vehicle that produces no harmful emissions at all - eg an electric or hydrogen fuel cell car. [See also: Hydrogen fuel cell]

Zuffenhausen
Where Porsches come from; the district in Stuttgart in which the production facility is located. Even though the Boxster and Cayman are built under contract by Valmet in Finland, Zuffenhausen is still seen as the spiritual home of the Porsche brand.

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