party vs reunion

party and reunion both are nouns.

Word	Noun	Adjective	Verb	Adverb
party	Yes	No	Yes	No
reunion	Yes	No	No	No

As nouns, reunion is a hyponym of party; that is, reunion is a word with a more specific, narrower meaning than party:

party (noun)	reunion (noun)
an occasion on which people can assemble for social interaction and entertainment	the act of coming together again
a gathering of people for pleasure	a party of former associates who have come together again
an organization to gain political power
a band of people associated temporarily in some activity
a person involved in legal proceedings

party (verb)	reunion (verb)
have or participate in a party