nightgown vs night-robe

nightgown and night-robe both are nouns.

Word	Noun	Adjective	Verb	Adverb
nightgown	Yes	No	No	No
night-robe	Yes	No	No	No

As nouns, nightgown and night-robe are synonyms defined as:

nightgown and night-robe: lingerie consisting of a loose dress designed to be worn in bed by women

Other synonyms of nightgown include gown, nightdress, nightie.

nightgown (noun)	night-robe (noun)
lingerie consisting of a loose dress designed to be worn in bed by women	lingerie consisting of a loose dress designed to be worn in bed by women