robe vs judge's robe

robe and judge's robe both are nouns.

Word	Noun	Adjective	Verb	Adverb
robe	Yes	No	Yes	No
judge's robe	Yes	No	No	No

As nouns, judge's robe is a hyponym of robe; that is, judge's robe is a word with a more specific, narrower meaning than robe:

robe: outerwear consisting of a long flowing garment used for official or ceremonial occasions
judge's robe: a gown worn by academics or judges

Other hyponyms of robe include academic gown, academic robe, vestment.

robe (noun)	judge's robe (noun)
any loose flowing garment	a gown worn by academics or judges
outerwear consisting of a long flowing garment used for official or ceremonial occasions

robe (verb)	judge's robe (verb)
clothe formally; especially in ecclesiastical robes
cover as if with clothing