building vs erection

building and erection both are nouns.

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

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

building (noun)	erection (noun)
the act of constructing something	the act of building or putting up
the commercial activity involved in repairing old structures or constructing new ones	a structure that has been erected
a structure that has a roof and walls and stands more or less permanently in one place	an erect penis
the occupants of a building