office block vs building

office block and building both are nouns.

Word	Noun	Adjective	Verb	Adverb
office block	Yes	No	No	No
building	Yes	No	No	No

As nouns, building is a hypernym of office block; that is, building is a word with a broader meaning than office block:

office block: a building containing offices where work is done
building: a structure that has a roof and walls and stands more or less permanently in one place

Other hypernyms of office block include edifice.

office block (noun)	building (noun)
a building containing offices where work is done	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