army vs army corps

army and army corps both are nouns.

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

army (noun)	army corps (noun)
a permanent organization of the military land forces of a nation or state	an army unit usually consisting of two or more divisions and their support
a large number of people united for some specific purpose