liaison vs affaire

liaison and affaire both are nouns.

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

As nouns, liaison and affaire are synonyms defined as:

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

liaison (noun)	affaire (noun)
a channel for communication between groups	a usually secretive or illicit sexual relationship
a usually secretive or illicit sexual relationship