heating system vs building

heating system and building both are nouns.

Word	Noun	Adjective	Verb	Adverb
heating system	Yes	No	No	No
building	Yes	No	No	No

heating system (noun)	building (noun)
utility to warm a building	the act of constructing something
	the commercial activity involved in repairing old structures or constructing new ones
	a structure that has a roof and walls and stands more or less permanently in one place
	the occupants of a building