corps vs army corps

corps and army corps both are nouns.

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

As nouns, corps and army corps are synonyms defined as:

corps and army corps: an army unit usually consisting of two or more divisions and their support

corps (noun)	army corps (noun)
an army unit usually consisting of two or more divisions and their support	an army unit usually consisting of two or more divisions and their support
a body of people associated together