affair vs involvement

affair and involvement both are nouns.

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

As nouns, affair and involvement are synonyms defined as:

affair and involvement: a usually secretive or illicit sexual relationship

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

affair (noun)	involvement (noun)
a vaguely specified concern	the act of sharing in the activities of a group
a formal or official social gathering or ceremony of people	a sense of concern with and curiosity about someone or something
a usually secretive or illicit sexual relationship	a connection of inclusion or containment
	a usually secretive or illicit sexual relationship
	the condition of sharing in common with others (as fellows or partners etc.)