vacation vs vacay

vacation and vacay both are nouns.

Word	Noun	Adjective	Verb	Adverb
vacation	Yes	No	Yes	No
vacay	Yes	No	No	No

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

Other hyponyms of vacation include half-term, vac, field day, outing, picnic, honeymoon, paid vacation, winter break.

vacation (noun)	vacay (noun)
the act of making something legally void	informal term for vacation
leisure time away from work devoted to rest or pleasure

vacation (verb)	vacay (verb)
spend or take a vacation