army corps vs army unit

army corps and army unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
army corps	Yes	No	No	No
army unit	Yes	No	No	No

As nouns, army unit is a hypernym of army corps; that is, army unit is a word with a broader meaning than army corps:

army corps: an army unit usually consisting of two or more divisions and their support
army unit: a military unit that is part of an army

army corps (noun)	army unit (noun)
an army unit usually consisting of two or more divisions and their support	a military unit that is part of an army