regular army vs ground forces

regular army and ground forces both are nouns.

Word	Noun	Adjective	Verb	Adverb
regular army	Yes	No	No	No
ground forces	Yes	No	No	No

As nouns, regular army and ground forces are synonyms defined as:

regular army and ground forces: a permanent organization of the military land forces of a nation or state

Other synonyms of regular army include army.

regular army (noun)	ground forces (noun)
a permanent organization of the military land forces of a nation or state	a permanent organization of the military land forces of a nation or state