army corps vs ROTC

army corps and ROTC both are nouns.

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

As nouns, ROTC is a hyponym of army corps; that is, ROTC is a word with a more specific, narrower meaning than army corps:

army corps: an army unit usually consisting of two or more divisions and their support
ROTC: a training program to prepare college students to be commissioned officers

Other hyponyms of army corps include WAC, Women's Army Corps, Reserve Officers Training Corps.

army corps (noun)	ROTC (noun)
an army unit usually consisting of two or more divisions and their support	a training program to prepare college students to be commissioned officers