black eye vs contusion

black eye and contusion both are nouns.

Word	Noun	Adjective	Verb	Adverb
black eye	Yes	No	No	No
contusion	Yes	No	No	No

As nouns, contusion is a hypernym of black eye; that is, contusion is a word with a broader meaning than black eye:

black eye: a swollen bruise caused by a blow to the eye
contusion: an injury that doesn't break the skin but results in some discoloration

Other hypernyms of black eye include bruise.

black eye (noun)	contusion (noun)
an unfortunate happening that hinders or impedes; something that is thwarting or frustrating	the action of bruising
a swollen bruise caused by a blow to the eye	an injury that doesn't break the skin but results in some discoloration
a bad reputation