Reference
Auto Parts Glossary
Not sure what a part is called? Here are plain-English definitions of the parts and terms we get asked about most.
- Aftermarket
- A part made by a third-party manufacturer to fit many vehicles, often at a lower price than OEM.
- Alternator
- The component that charges the battery and powers the electrical system while the engine runs.
- Ball joint
- A pivoting connection between the control arm and steering knuckle; wear causes clunks and play.
- Brake drum
- A drum-shaped component used in drum brake systems that brake shoes press against from the inside.
- Brake pads
- Friction material that presses against the rotor to slow the wheel; a common wear item.
- Cabin air filter
- Filters the air entering the passenger compartment through the HVAC system.
- Caliper
- The component that squeezes the brake pads against the rotor using hydraulic pressure.
- Catalytic converter
- An exhaust component that reduces harmful emissions; required and often expensive to replace.
- Control arm
- A suspension link that connects the wheel hub to the vehicle frame.
- Coolant / antifreeze
- The fluid that absorbs engine heat and resists freezing and boiling; must be mixed for the climate.
- Fitment
- Whether a part correctly fits a specific vehicle’s year, make, model, trim, and engine.
- Ignition coil
- Converts battery voltage into the high voltage needed to fire the spark plugs.
- Muffler
- Reduces exhaust noise; rust and holes cause a loud or rattling exhaust.
- OEM
- Original Equipment Manufacturer — a part made by or for the vehicle’s brand, matching the original exactly.
- Oxygen sensor
- A sensor that measures exhaust oxygen to help the engine run efficiently; a common cause of a check-engine light.
- Radiator
- The heat exchanger that cools the engine’s coolant using airflow.
- Rotor
- The metal disc the brake pads clamp onto; can warp or wear and may need resurfacing or replacement.
- Serpentine belt
- A single belt that drives multiple accessories (alternator, water pump, A/C); cracks and glazing signal replacement.
- Solenoid
- An electromagnetic switch — in a starter, it engages the motor and routes power to crank the engine.
- Spark plug
- Ignites the air-fuel mixture in the engine; worn plugs cause misfires and poor fuel economy.
- Starter
- The motor that cranks the engine to start it when you turn the key or press the button.
- Strut
- A structural suspension component combining a shock absorber and spring support; affects ride and handling.
- Thermostat
- A valve that regulates coolant flow to keep the engine at its proper operating temperature.
- Tie rod end
- Connects the steering system to the wheel; wear causes loose steering and uneven tire wear.
- Timing belt
- A belt that keeps the engine’s valves and pistons in sync; failure can cause major engine damage.
- Trim
- A specific version of a model (e.g., LX, EX, Sport) that can change which parts fit.
- VIN
- Vehicle Identification Number — a 17-character code that uniquely identifies how your vehicle was built; the most reliable way to confirm part fitment.
- Water pump
- Circulates coolant through the engine and radiator to prevent overheating.
- Wheel cylinder
- In drum brakes, the hydraulic part that pushes the brake shoes outward against the drum.