facial gesture vs smile

facial gesture and smile both are nouns.

Word	Noun	Adjective	Verb	Adverb
facial gesture	Yes	No	No	No
smile	Yes	No	Yes	No

As nouns, smile is a hyponym of facial gesture; that is, smile is a word with a more specific, narrower meaning than facial gesture:

facial gesture: a gesture executed with the facial muscles
smile: a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

Other hyponyms of facial gesture include emoticon, gape, face, grimace, frown, scowl, grin, grinning, smiling, laugh, snarl, straight face, wink, wince.

facial gesture (noun)	smile (noun)
a gesture executed with the facial muscles	a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

facial gesture (verb)	smile (verb)
	change one's facial expression by spreading the lips, often to signal pleasure
	express with a smile