gem vs corn muffin

gem and corn muffin both are nouns.

Word	Noun	Adjective	Verb	Adverb
gem	Yes	No	No	No
corn muffin	Yes	No	No	No

As nouns, corn muffin is a hyponym of gem; that is, corn muffin is a word with a more specific, narrower meaning than gem:

Other hyponyms of gem include bran muffin, popover.

gem (noun)	corn muffin (noun)
a precious or semiprecious stone incorporated into a piece of jewelry	cornbread muffin
art highly prized for its beauty or perfection
a sweet quick bread baked in a cup-shaped pan
a person who is as brilliant and precious as a piece of jewelry
a crystalline rock that can be cut and polished for jewelry