building vs staircase

building and staircase both are nouns.

Word	Noun	Adjective	Verb	Adverb
building	Yes	No	No	No
staircase	Yes	No	No	No

building (noun)	staircase (noun)
the act of constructing something	a way of access (upward and downward) consisting of a set of steps
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