affair vs liaison

affair and liaison both are nouns.

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

As nouns, affair and liaison are synonyms defined as:

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

affair (noun)	liaison (noun)
a vaguely specified concern	a channel for communication between groups
a formal or official social gathering or ceremony of people	a usually secretive or illicit sexual relationship
a usually secretive or illicit sexual relationship