In short: One move by one of the players. A full move in notation, like 1. e4 e5, is made up of two plies.
Also called half-move.
The word move is used in two ways. Sometimes a move is one player's turn: White makes a move, Black replies with a move. Sometimes a move is White's and Black's turns together, the way the moves are numbered. To tell them apart, a single player's turn is called a ply, or a half-move.
In notation
1. e4 e5 is one move but two plies: White played e4 and Black e5. The next move, 2. Nf3, has the number 2, and Black's reply belongs to the same number. When a Black move is written on its own, three dots follow the number: 2... Nc6.
In the rules
When the rules count moves, they usually mean moves by each player. 40 moves in two hours means that each player must make 40 moves of their own. The fifty-move rule applies when the last 50 moves by each player have been made without a capture and without a pawn move, so 100 plies. Read about the draw.
A FEN has a counter for exactly the plies since the last capture or pawn move, and a number for the move the game has reached.
Frequently asked questions
Is a ply the same as a half-move?
Yes. Both words mean one turn by one player.
Does the fifty-move rule count moves or plies?
Moves. It applies when the last 50 moves by each player have been made without a capture and without a pawn move, so 100 plies.
Updated November 14, 2026