wedding dress vs wedding gown

wedding dress and wedding gown both are nouns.

Word	Noun	Adjective	Verb	Adverb
wedding dress	Yes	No	No	No
wedding gown	Yes	No	No	No

As nouns, wedding dress and wedding gown are synonyms defined as:

Other synonyms of wedding dress include bridal gown.

wedding dress (noun)	wedding gown (noun)
a gown worn by the bride at a wedding	a gown worn by the bride at a wedding