viola da gamba vs viol

viola da gamba and viol both are nouns.

Word	Noun	Adjective	Verb	Adverb
viola da gamba	Yes	No	No	No
viol	Yes	No	No	No

As nouns, viol is a hypernym of viola da gamba; that is, viol is a word with a broader meaning than viola da gamba:

viola da gamba: viol that is the bass member of the viol family with approximately the range of the cello
viol: any of a family of bowed stringed instruments that preceded the violin family

viola da gamba (noun)	viol (noun)
viol that is the bass member of the viol family with approximately the range of the cello	any of a family of bowed stringed instruments that preceded the violin family