troops vs garrison

troops and garrison both are nouns.

Word	Noun	Adjective	Verb	Adverb
troops	Yes	No	No	No
garrison	Yes	No	Yes	No

As nouns, garrison is a hyponym of troops; that is, garrison is a word with a more specific, narrower meaning than troops:

Other hyponyms of troops include friendly, hostile, cavalry, horse, horse cavalry.

troops (noun)	garrison (noun)
soldiers collectively	a fortified military post where troops are stationed
	the troops who maintain and guard a fortified place

troops (verb)	garrison (verb)
	station (troops) in a fort or garrison