Green Beret vs soldier

Green Beret and soldier both are nouns.

Word	Noun	Adjective	Verb	Adverb
Green Beret	Yes	No	No	No
soldier	Yes	No	Yes	No

As nouns, soldier is a hypernym of Green Beret; that is, soldier is a word with a broader meaning than Green Beret:

Green Beret: a soldier who is a member of the United States Army Special Forces
soldier: an enlisted man or woman who serves in an army

Green Beret (noun)	soldier (noun)
a soldier who is a member of the United States Army Special Forces	a wingless sterile ant or termite having a large head and powerful jaws adapted for defending the colony
	an enlisted man or woman who serves in an army

Green Beret (verb)	soldier (verb)
	serve as a soldier in the military