棋子 (qízǐ) means "chess piece" or "game piece" and refers to the individual pieces used in board games such as Chinese chess (象棋) or Go (围棋). It combines 棋 (chess/board game) and 子 (piece/seed). It can also be used figuratively to mean "pawn" in a larger scheme.
他把棋子一个一个摆好,准备开始下棋。
tā bǎ qízǐ yī gè yī gè bǎi hǎo, zhǔnbèi kāishǐ xià qí.
He arranged the chess pieces one by one, getting ready to start playing.
你少了一个棋子,没法下了。
nǐ shǎo le yī gè qízǐ, méi fǎ xià le.
You're missing a chess piece, so you can't play.
这副象棋的棋子是用木头做的。
zhè fù xiàngqí de qízǐ shì yòng mùtou zuò de.
The pieces of this chess set are made of wood.