knuckles vs knucks

knuckles and knucks both are nouns.

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

As nouns, knuckles and knucks are synonyms defined as:

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

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

knuckles (noun)	knucks (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