cylinder vs brake drum

cylinder and brake drum both are nouns.

Word	Noun	Adjective	Verb	Adverb
cylinder	Yes	No	No	No
brake drum	Yes	No	No	No

As nouns, brake drum is a hyponym of cylinder; that is, brake drum is a word with a more specific, narrower meaning than cylinder:

cylinder: a surface generated by rotating a parallel line around a fixed line
brake drum: a hollow cast iron cylinder attached to the wheel that forms part of the brakes

Other hyponyms of cylinder include drum, shank, shank, shank, stem, stalactite, stalagmite, barrel, drum, pipe, tube.

cylinder (noun)	brake drum (noun)
a cylindrical container for oxygen or compressed air	a hollow cast iron cylinder attached to the wheel that forms part of the brakes
a chamber within which piston moves
a surface generated by rotating a parallel line around a fixed line
a solid bounded by a cylindrical surface and two parallel planes (the bases)