ground forces vs regular army

ground forces and regular army both are nouns.

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

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

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

Other synonyms of ground forces include army.

ground forces (noun)	regular army (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