church vs church building

church and church building both are nouns.

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

As nouns, church and church building are synonyms defined as:

church and church building: a place for public (especially Christian) worship

church (noun)	church building (noun)
a service conducted in a house of worship	a place for public (especially Christian) worship
a place for public (especially Christian) worship
one of the groups of Christians who have their own beliefs and forms of worship
the body of people who attend or belong to a particular local church

church (verb)	church building (verb)
perform a special church rite or service for