noun
A piece broken off from a larger whole; often used for physical fragments.
割れた皿の片割れが床に落ちていた。
A fragment of the broken plate was lying on the floor.
noun
accomplice; confederate; one of the same group
Refers to a member of a group, often with a negative connotation of being in cahoots; used for partners in crime or fellow members of a dubious group.
犯人の片割れがまだ捕まっていない。
The accomplice of the criminal has not been caught yet.
noun
One item from a matched set, such as a shoe, glove, or earring; also used figuratively for a counterpart or the other half of a pair.
靴下の片割れがどこかに行ってしまった。
One of the socks has gone missing.
破片 is a more common and neutral word for 'fragment' or 'broken piece', while 片割れ often implies a piece that was once part of a whole and may carry a nuance of incompleteness or pairing.
仲間 is a general word for 'companion' or 'colleague' without the negative connotation that 片割れ can have when referring to an accomplice.
Compound of 片 (kata, 'one side') + 割れ (ware, 'broken piece'), from the verb 割れる (wareru, 'to break'). The spelling 片破れ is a rare variant using 破 (ha, 'tear/break').