military service vs military

military service and military both are nouns.

Word	Noun	Adjective	Verb	Adverb
military service	Yes	No	No	No
military	Yes	Yes	No	No

military service (noun)	military (noun)
land tenure by service in the lord's army	the military forces of a nation
a force that is a branch of the armed forces

military service (adjective)	military (adjective)
	associated with or performed by members of the armed services as contrasted with civilians
	characteristic of or associated with soldiers or the military
	of or relating to the study of the principles of warfare