grimace vs smile

grimace and smile both are nouns.

Word	Noun	Adjective	Verb	Adverb
grimace	Yes	No	Yes	No
smile	Yes	No	Yes	No

As verbs, smile is a hyponym of grimace; that is, smile is a word with a more specific, narrower meaning than grimace:

grimace: contort the face to indicate a certain mental or emotional state
smile: change one's facial expression by spreading the lips, often to signal pleasure

Other hyponyms of grimace include squinch, squint, wince, frown, glower, lour, lower, screw up, mop, mow, pout.

grimace (noun)	smile (noun)
a contorted facial expression	a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

grimace (verb)	smile (verb)
contort the face to indicate a certain mental or emotional state	change one's facial expression by spreading the lips, often to signal pleasure
	express with a smile