get together vs occasion

get together and occasion both are nouns.

Word	Noun	Adjective	Verb	Adverb
get together	Yes	No	Yes	No
occasion	Yes	No	Yes	No

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

Other hypernyms of get together include affair, function, social affair, social function, social gathering, social occasion.

get together (noun)	occasion (noun)
a small informal social gathering	an event that occurs at a critical time
	a formal or official social gathering or ceremony of people
	a rational motive for a belief or action
	an opportunity to do something
	the time of a particular event

get together (verb)	occasion (verb)
get together socially or for a specific purpose	give occasion to
become part of; become a member of a group or organization
get people together