night-robe vs nightie

night-robe and nightie both are nouns.

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

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

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

Other synonyms of night-robe include gown, nightdress, nightgown.

night-robe (noun)	nightie (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