noun
promoted piece; promotion (shogi)
Shogi term for a piece that has been promoted upon reaching the opponent's camp. Refers to the state or the piece itself.
See also: 成る
歩が成りになって、と金になった。
The pawn promoted and became a tokin.
成りの駒は動きが変わる。
A promoted piece moves differently.
成る is the verb 'to be promoted' (intransitive); 成り is the noun form referring to the promoted state or piece.
Noun form of the verb 成る (なる, 'to become; to be promoted'), used specifically in shogi for a promoted piece.