armed forces vs armed

armed forces is a noun but armed is not a noun.

Word	Noun	Adjective	Verb	Adverb
armed forces	Yes	No	No	No
armed	No	Yes	No	No

armed forces (noun)	armed (noun)
the military forces of a nation

armed forces (adjective)	armed (adjective)
	(used of persons or the military) characterized by having or bearing arms
	(used of plants and animals) furnished with bristles and thorns
	having arms or arms as specified; used especially in combination