grotto vs cave

grotto and cave both are nouns.

Word	Noun	Adjective	Verb	Adverb
grotto	Yes	No	No	No
cave	Yes	No	Yes	No

As nouns, cave is a hypernym of grotto; that is, cave is a word with a broader meaning than grotto:

grotto: a small cave (usually with attractive features)
cave: a geological formation consisting of an underground enclosure with access from the surface of the ground or from the sea

grotto (noun)	cave (noun)
a small cave (usually with attractive features)	a geological formation consisting of an underground enclosure with access from the surface of the ground or from the sea

grotto (verb)	cave (verb)
	explore natural caves
	hollow out as if making a cave or opening