When was the last time you bought a new car? If you're like most Americans, you venture into a new-car dealer's showroom once every three to five years. Problem is, cars evolve pretty fast, and the language used to describe them does, too. See an ad on TV, read a brochure or listen to a sales spiel, and you almost need a translator to figure it out. It doesn't help that different carmakers use different terms for the same thing.

To help, we offer a kind of crash course in current car-speak. It includes terms that have emerged in the last few years and a few older ones that still cause confusion. Of course, you'll probably need a whole new list in a couple of years.

Active suspension: A system incorporating hydraulic pumps and sensors to automatically change the internal pressure of sophisticated shock absorbers in response to bumps, weight transfer during cornering, cargo and passenger load and other factors. By increasing or releasing hydraulic pressure at each of the four wheels as necessary, it smooths out a vehicle's ride and minimizes body roll on curves.

Adjustable suspension: A system that allows the driver to control the firmness of the shock absorbers with the flip of a switch, from soft (to smooth out bumps) to firm (to reduce body lean while cornering).

AWD (all-wheel drive): A drivetrain that powers all four wheels all the time. The driver cannot switch to two-wheel drive. Found most commonly on vehicles not intended for off-roading, AWD provides the extra traction of four-wheel drive but lacks a low-speed transfer case needed for rugged terrain. Compare "four-wheel drive."

Brake assist: An electronically controlled system that reduces stopping distance by as much as 20 percent in an emergency. When sensors recognize the driver's intent to initiate a panic stop, the system automatically applies continuous, full braking force. Brake assist also counteracts some drivers' tendency to ease up on the pedal and thereby deactivate anti-lock brakes.

Crossover: A vehicle that combines design characteristics or functional elements from two or more types of vehicles. Examples include the Chevrolet SSR (a sports car with the cargo bed of a pickup), Ford Explorer Sport Trac (a sport-utility vehicle with a pickup bed) and CUVs (see next definition).

CUV (crossover utility vehicle): A vehicle built on the platform of a car with the wagon-like body of an SUV, having either a tailgate or liftgate. Traditional SUVs such as the Ford Explorer or Chevrolet Suburban are built on a truck chassis with body-on-frame construction, but CUVs have a body and chassis made as a single unit (so-called unibody construction). Usually, they have all-wheel drive but may also offer front-wheel drive. Examples include the Ford Freestyle, Toyota Highlander and Volvo XC90.

CVT (continuously variable transmission): A transmission using an arrangement of belts and pulleys rather than gears. A conventional transmission has a fixed number of gears to transfer engine power to the drive wheels, according to specific gear ratios (the number of revolutions a gear must make to turn a different-size gear one revolution). The gear ratios determine the vehicle's acceleration and other performance characteristics. Because a CVT uses pulleys and belts that move smoothly along an axis, it theoretically has an infinite range of gear ratios, allowing greater efficiency in translating engine speed to vehicle speed. Because of their greater efficiency, CVTs can improve fuel economy by as much as 10 percent compared with a conventional transmission.

ESC (electronic stability control): See "stability control."

ESP (electronic stability program): See "stability control."

Four-wheel drive (4WD): A drivetrain that sends power to all four wheels, usually through a transfer case. Part-time four-wheel drive can operate only on slippery surfaces; because it has no center differential (which allows the front wheels and rear wheels to turn at different rates), a part-time four-wheel-drive system can damage the tires and other components when used on dry pavement. Full-time four-wheel drive incorporates a center differential, so the vehicle can switch from two-wheel drive to four-wheel drive anytime, anywhere, either manually (when the driver decides) or automatically (when sensors detect wheel slippage). Permanent 4WD sends power to all wheels, all the time; it differs from all-wheel drive in that it includes a two-speed transfer case, allowing the driver to choose between 4WD High (for normal driving) and 4WD Low (for off-roading). Compare "AWD."

Side airbag: A safety device designed to protect an occupant's head, torso or both in a side-impact crash. Those that protect only the torso or both the torso and head may deploy from the seat, the roof pillar or the door. Those that protect only the head--often referred to as "curtain airbags"or "air curtains"--deploy from the headliner. Studies show that side airbags offering head protection significantly reduce deaths in side-impact crashes compared with torso-only types or no side airbags at all.

Stability control: An extension of traction control technology that helps you maintain control on a turn. Using sensors that recognize the vehicle's side-to-side motion with respect to its intended path of travel, the system detects an incipient skid and applies the brake to a single wheel as necessary. Recent studies show that stability control significantly reduces the risk of serious single-vehicle, run-off-the-road crashes.

Telematics: A package of integrated electronics, including a global positioning system and wireless phone, which can provide on-screen mapping and guidance in the vehicle and automatically summon emergency medical personnel in a crash.

Traction control: An extension of anti-lock brake technology that detects wheel spin on slippery surfaces and selectively applies the brake to the drive wheel with the least traction. Some traction control systems reduce engine power in addition to braking one wheel. The feature helps you get going from a dead stop on slippery surfaces or maintain control on wet or icy roads.

Variable-assist steering: A power steering enhancement that varies the effort necessary to turn the wheel, depending on the vehicle's speed. Steering requires more effort at higher speeds (for better road feel during highway cruising) and less effort at low speeds (for easier parking).