middle ear vs cavity

middle ear and cavity both are nouns.

Word	Noun	Adjective	Verb	Adverb
middle ear	Yes	No	No	No
cavity	Yes	No	No	No

As nouns, cavity is a hypernym of middle ear; that is, cavity is a word with a broader meaning than middle ear:

middle ear: the main cavity of the ear; between the eardrum and the inner ear
cavity: (anatomy) a natural hollow or sinus within the body

Other hypernyms of middle ear include bodily cavity, cavum.

middle ear (noun)	cavity (noun)
the main cavity of the ear; between the eardrum and the inner ear	(anatomy) a natural hollow or sinus within the body
	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