social occasion vs social event

social occasion and social event both are nouns.

Word	Noun	Adjective	Verb	Adverb
social occasion	Yes	No	No	No
social event	Yes	No	No	No

As nouns, social event is a hypernym of social occasion; that is, social event is a word with a broader meaning than social occasion:

social occasion: a formal or official social gathering or ceremony of people
social event: an event characteristic of persons forming groups

Other hypernyms of social occasion include assemblage, gathering.

social occasion (noun)	social event (noun)
a formal or official social gathering or ceremony of people	an event characteristic of persons forming groups