cavity vs fire pit

cavity and fire pit both are nouns.

Word	Noun	Adjective	Verb	Adverb
cavity	Yes	No	No	No
fire pit	Yes	No	No	No

As nouns, fire pit is a hyponym of cavity; that is, fire pit is a word with a more specific, narrower meaning than cavity:

Other hyponyms of cavity include trou-de-loup, barbecue pit, borrow pit, divot, quicksand, sandpit, sawpit, tar pit.

cavity (noun)	fire pit (noun)
(anatomy) a natural hollow or sinus within the body	a pit whose floor is incandescent lava
a sizeable hole (usually in the ground)
soft decayed area in a tooth; progressive decay can lead to the death of a tooth
space that is surrounded by something