twitching vs twitch

twitching and twitch both are nouns.

Word	Noun	Adjective	Verb	Adverb
twitching	Yes	No	No	No
twitch	Yes	No	Yes	No

As nouns, twitching and twitch are synonyms defined as:

twitching and twitch: a sudden muscle spasm; especially one caused by a nervous condition

Other synonyms of twitching include vellication.

twitching (noun)	twitch (noun)
a sudden muscle spasm; especially one caused by a nervous condition	a sudden muscle spasm; especially one caused by a nervous condition

twitching (verb)	twitch (verb)
	make an uncontrolled, short, jerky motion
	squeeze tightly between the fingers
	move or pull with a sudden motion
	toss with a sharp movement so as to cause to turn over in the air
	move with abrupt, seemingly uncontrolled motions