party vs open house

party and open house both are nouns.

Word	Noun	Adjective	Verb	Adverb
party	Yes	No	Yes	No
open house	Yes	No	No	No

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

party (noun)	open house (noun)
an occasion on which people can assemble for social interaction and entertainment	an informal party of people with hospitality for all comers
a gathering of people for pleasure
an organization to gain political power
a band of people associated temporarily in some activity
a person involved in legal proceedings

party (verb)	open house (verb)
have or participate in a party