knucks vs knuckles

knucks and knuckles both are nouns.

Word	Noun	Adjective	Verb	Adverb
knucks	Yes	No	No	No
knuckles	Yes	No	No	No

As nouns, knucks and knuckles are synonyms defined as:

knucks and knuckles: (used in the plural) a small metal weapon; worn over the knuckles on the back of the hand

Other synonyms of knucks include brass knuckles, brass knucks, knuckle duster.

knucks (noun)	knuckles (noun)
(used in the plural) a small metal weapon; worn over the knuckles on the back of the hand	(used in the plural) a small metal weapon; worn over the knuckles on the back of the hand