vestment vs cassock

vestment and cassock both are nouns.

Word	Noun	Adjective	Verb	Adverb
vestment	Yes	No	No	No
cassock	Yes	No	No	No

As nouns, cassock is a hyponym of vestment; that is, cassock is a word with a more specific, narrower meaning than vestment:

vestment: gown (especially ceremonial garments) worn by the clergy
cassock: a black garment reaching down to the ankles; worn by priests or choristers

Other hyponyms of vestment include alb, chasuble, humeral veil, veil, pallium, pontifical, surplice.

vestment (noun)	cassock (noun)
gown (especially ceremonial garments) worn by the clergy	a black garment reaching down to the ankles; worn by priests or choristers