troops vs horse cavalry

troops and horse cavalry both are nouns.

Word	Noun	Adjective	Verb	Adverb
troops	Yes	No	No	No
horse cavalry	Yes	No	No	No

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

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

troops (noun)	horse cavalry (noun)
soldiers collectively	an army unit mounted on horseback
	troops trained to fight on horseback