dinner gown vs evening gown

dinner gown and evening gown both are nouns.

Word	Noun	Adjective	Verb	Adverb
dinner gown	Yes	No	No	No
evening gown	Yes	No	No	No

As nouns, dinner gown and evening gown are synonyms defined as:

Other synonyms of dinner gown include dinner dress, formal.

dinner gown (noun)	evening gown (noun)
a gown for evening wear	a gown for evening wear