brake drum vs cylinder

brake drum and cylinder both are nouns.

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

As nouns, cylinder is a hypernym of brake drum; that is, cylinder is a word with a broader meaning than brake drum:

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

brake drum (noun)	cylinder (noun)
a hollow cast iron cylinder attached to the wheel that forms part of the brakes	a cylindrical container for oxygen or compressed air
	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)