This question and its answers list the names of bike parts and cycling concepts.
Some Rules
- Make sure you only put one term per answer!
- Try to include an image if applicable
- Include sources that contain detailed information
- Add a link to the index in this question using edit.
Also, I made this a community wiki, so that anyone will be able to edit it, and to stop rep-hoarding
There's a handy reference at the Park Tool Co. website, a bike repair map; it's a diagram of a bike with all the parts labeled, and is very handy! At the moment, the diagram is up at parktool.com/blog/repair-help. (They've changed the URL in the past, so this link may break.)
A road bike has the following parts (source):
A mountain bike has the following parts (source):
Edit: This page is meant to identify what things or concepts are (as per this thread in meta). If you want to recommend an accessory or a specific product you've found handy, please use the accessories page.
Contents:
Axle
Axle Nuts
BCD (Bolt Circle Diameter)
Bearing
Bonk/Bonking
Bottle Cage / Bottle Holder
Bottom Bracket
Brazed Frame
Brifter
BSO/Bike-Shaped-Object
Cable Pull
Cable Stretcher
Cadence
Chain Gauge
Chain Guard/Cover
Chain Tool
Chain Tug/Chain Tensioner
Chainstay Length
Chainsuck
Chamois
Clipless Pedals
Coaster Brake (foot brake / pedal brake)
Crank
Derailleur
Derailer Hanger/Derailleur Ranger
Disc Hub
Door Zone
Dropout
Dropper Post
Dunlop Valve
Fender/Mudguard/Mudflaps
Fixed-Gear
Flip-Flop Hub
Folding Bike
Frame
Gear Inches
Groupset
Handlebars
Headset
Hose Clamp aka Jubilee Clip
Hub
Hub Skewer
Internally-Geared Hub
Lawyer lips/lawyer tabs
LBS/Local Bike Shop
Luggage Carrier/Rack
Lugged Frame
Master Link
Mixte
Mountain Bike
Pannier
Play
Power Meter
Presta Valve/Presta Tube
Pump Peg
Q-Factor
Quick-Release
REI (Recreational Equipment Inc)
Rim
Rim Tape
Saddle
Saddlebag
Schrader Valve/ Schrader Tube
Single-speed
Skewer
Spider
Spoke
Stem
Suspension Fork/Rear Shock
Through/Thru Axle
Tire Clearance
Tire Lever/Tire Iron
Tire Saver
Track Pump/Floor Pump
Triathalon Bars/Triathlon Bars
Welded Frame