occasion vs affair

occasion and affair both are nouns.

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

As nouns, occasion and affair are synonyms defined as:

occasion and affair: a formal or official social gathering or ceremony of people

Other synonyms of occasion include function, social affair, social function, social gathering, social occasion.

occasion (noun)	affair (noun)
an event that occurs at a critical time	a vaguely specified concern
a formal or official social gathering or ceremony of people	a formal or official social gathering or ceremony of people
a rational motive for a belief or action	a usually secretive or illicit sexual relationship
an opportunity to do something
the time of a particular event

occasion (verb)	affair (verb)
give occasion to