affair vs intimacy

affair and intimacy both are nouns.

Word	Noun	Adjective	Verb	Adverb
affair	Yes	No	No	No
intimacy	Yes	No	No	No

As nouns, affair and intimacy are synonyms defined as:

Other synonyms of affair include affaire, amour, involvement, liaison.

affair (noun)	intimacy (noun)
a vaguely specified concern	close or warm friendship
a formal or official social gathering or ceremony of people	a feeling of being intimate and belonging together
a usually secretive or illicit sexual relationship	a usually secretive or illicit sexual relationship