Aftermarket: Parts or accessories not supplied from the original bicycle manufacture.

Bottom Bracket: The bearings and spindle, located in the lowest part of the frame, to which the crank is connected.

Center-pull Brake: A brake in which the main cable runs down the center line of breaking device and pulls the pressure from the center of the brake. This type of brake was popular from the late 1960's to the early 1980's. Center-pull brakes are a good choice for bicycles that have a long reach from the mounting point to the rim. See photo below.

Chain: Modern bicycles use a roller chain to connect the crank to the rear drive wheel. Chain drives are among the most efficient means of power transmission known.

Chain Guard: Any of several types of protective baffle device used to prevent the bicycle chain from entrapping a riders pants leg, or soiling the cyclist's leg or clothing. Getting your clothing caught in a bicycle chain can be an inconvenience on any bike, and in some cases very dangerous. See photo below.

Coaster Brake: A type of rear bicycle hub that incorporates an internal brake which is operated by the rider pedaling or pushing backwards. Called a "coaster brake" because it combines the functions of the brake and freewheel ("coaster") in a single unit.

Crank: The arm which connects the pedals to the bottom bracket axle. Sometimes called a "crank arm." In simple terms, the crank is used to turn the front sprocket and power the chain to the rear wheel.

1 -piece Crank: A one-piece crank consists of a single steel forging axle-type device which allows the bicycle rider to turn the chain and propel the bike. Installed through the frame and connected to the front sprocket. One piece cranks are commonly found on older American made bicycles, and many current low-end bikes. See photo below.

3 -piece Crank: Nowadays many bicycles are equipped with a three-piece crank. A three-piece type crank consists of three pieces; the left arm crank, the center axle, and the right arm crank. Installed into the frame and connected to the front sprocket, three-piece cranks use either cotters or tapered cotterless attachments. Generally much stronger than a one-piece crank, the three-piece is also more expensive to produce. See photo below.

Fixed-Gear or "Fixie: A rear drive system that lacks a freewheel, meaning you can't coast without the crank turning. There usually is only a single gear ratio.

Frame: The skeleton of a bicycle to which the wheels and most other parts are connected. See photo below.

Frame size: The height of the bicycle based on measuring the size of the seat post tube. Read more here.

Hand brake: A brake that slows the bike via hand pressure or squeezing a lever attached to the handlebars

Handlebar or Handlebars: Handlebars are the wide (mostly) chrome tubes that attach to the top of the forks allowing the rider to turn the bicycle. See photo below.

Kickstand: A steel prop for holding a bicycle upright while parked. They are called "kickstands" because they are operated by the foot. See photo below.

Lug or Lugged (frame): A short angled tube used to join and reinforce two or more tubes of a bicycle frame. Generally known to improve the overall strength of the bike frame. See photo below.

Pedal or Pedals: Connected to the crank arms, the pedal is the part you put your foot on. The axles of the pedals are threaded into the crank.

Quick-release lever: A single lever used on wheel hubs, and sometimes seat posts, which replaces the locknut for quick and easy, no-tool removal or adjustment. See photo below.

Saddle: A bicycle seat.

Seat Post: The removable tube that the saddle mounts onto.

Seat Tube: The frame tube that connects between the top tube and the bottom bracket. The seat post inserts into the top of the seat tube.

Single-Speed: While any bike that doesn't have multiple gears or speeds is technically called a "single-speed" bicycle, this term generally refers to a bike with a one-speed freewheel and coaster brakes.

Spoke or Spokes: One of the wires connecting the outside wheel to the hub of a bicycle. A conventional spoke has a head, appearing somewhat like the head of a nail, to keep it from pulling through the bicycle hub. On the other end the spoke is threaded, and a special adjusting nut is attached and fits through the wheel.