headroom vs room

headroom and room both are nouns.

Word	Noun	Adjective	Verb	Adverb
headroom	Yes	No	No	No
room	Yes	No	Yes	No

As nouns, room is a hypernym of headroom; that is, room is a word with a broader meaning than headroom:

Other hypernyms of headroom include elbow room, way.

headroom (noun)	room (noun)
the capacity of a system to reproduce loud sounds without distortion	an area within a building enclosed by walls and floor and ceiling
vertical space available to allow easy passage under something	the people who are present in a room
	space for movement
	opportunity for

headroom (verb)	room (verb)
	live and take one's meals at or in