Cage

[1] Any enclosure.
[2] On a front derailleur of a bicycle, it is a pair of parallel plates that push the chain from side to side; on a rear derailleur, it is a set of plates in which pulleys are mounted to hold and guide the chain from cog to cog.
[3] Any device for holding or securing something, e.g., a bottle cage on a bicycle.
[4] When referring to bearings, it is the part which holds the balls or rollers in place. Usually called ball cage.
See also bearing cage, needle cage, roller cage
[5] When referring to a vehicle, it is the safety enclosure called a "roll cage". Seedifferential cage, integrated roll cage, multi-reed cage
[6] The platform on which goods are hoisted up or lowered down a vertical shaft or guides; in mines, the steel box used to raise and lower workers, materials, or tubs. May have two or three decks.