grin vs grinning

grin and grinning both are nouns.

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

As nouns, grin and grinning are synonyms defined as:

grin and grinning: a facial expression characterized by turning up the corners of the mouth; usually shows pleasure or amusement

Other synonyms of grin include smile, smiling.

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

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