Silver Star Medal vs medallion

Silver Star Medal and medallion both are nouns.

Word	Noun	Adjective	Verb	Adverb
Silver Star Medal	Yes	No	No	No
medallion	Yes	No	No	No

As nouns, medallion is a hypernym of Silver Star Medal; that is, medallion is a word with a broader meaning than Silver Star Medal:

Silver Star Medal: a United States military decoration for gallantry in action
medallion: an award for winning a championship or commemorating some other event

Other hypernyms of Silver Star Medal include decoration, laurel wreath, medal, palm, ribbon.

Silver Star Medal (noun)	medallion (noun)
a United States military decoration for gallantry in action	an award for winning a championship or commemorating some other event
	an emblem indicating that a taxicab is registered
	a circular helping of food (especially a boneless cut of meat)
	a circular helping of food (especially a boneless cut of meat) "medallions of veal"
	any of various large ancient Greek coins