dinner vs dinner party

dinner and dinner party both are nouns.

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

As nouns, dinner and dinner party are synonyms defined as:

dinner and dinner party: a party of people assembled to have dinner together

dinner (noun)	dinner party (noun)
the main meal of the day served in the evening or at midday	a party of people assembled to have dinner together
a party of people assembled to have dinner together