dinner party vs dinner

dinner party and dinner both are nouns.

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

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

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

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