standing army vs ground forces

standing army and ground forces both are nouns.

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

As nouns, ground forces is a hypernym of standing army; that is, ground forces is a word with a broader meaning than standing army:

standing army: a permanent army of paid soldiers
ground forces: a permanent organization of the military land forces of a nation or state

Other hypernyms of standing army include army, regular army.

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