smirk vs grin

smirk and grin both are nouns.

Word	Noun	Adjective	Verb	Adverb
smirk	Yes	No	Yes	No
grin	Yes	No	Yes	No

As nouns, grin is a hypernym of smirk; that is, grin is a word with a broader meaning than smirk:

smirk: a smile expressing smugness or scorn instead of pleasure
grin: a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

Other hypernyms of smirk include grinning, smile, smiling.

smirk (noun)	grin (noun)
a smile expressing smugness or scorn instead of pleasure	a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

smirk (verb)	grin (verb)
smile affectedly or derisively	to draw back the lips and reveal the teeth, in a smile, grimace, or snarl