room vs standing room

room and standing room both are nouns.

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

As nouns, standing room is a hyponym of room; that is, standing room is a word with a more specific, narrower meaning than room:

room (noun)	standing room (noun)
an area within a building enclosed by walls and floor and ceiling	room for passengers or spectators to stand
the people who are present in a room
space for movement
opportunity for

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