muffin vs popover

muffin and popover both are nouns.

Word	Noun	Adjective	Verb	Adverb
muffin	Yes	No	No	No
popover	Yes	No	No	No

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

muffin: a sweet quick bread baked in a cup-shaped pan
popover: light hollow muffin made of a puff batter (individual Yorkshire pudding) baked in a deep muffin cup

Other hyponyms of muffin include bran muffin, corn muffin.

muffin (noun)	popover (noun)
a sweet quick bread baked in a cup-shaped pan	light hollow muffin made of a puff batter (individual Yorkshire pudding) baked in a deep muffin cup