1. A checkmate where the king is surrounded by its own pieces and is unable to move.

1. A move in chess where a player willingly offers up a piece or pawn to gain a positional or tactical advantage.

2. A position in chess where two kings face each other with only one square in between.

3. A chess piece that can move any number of vacant squares horizontally or vertically.

4. A tactic in chess where a piece is moved, revealing a direct attack by another piece behind it.

5. The position in which a player's king is threatened with capture and there is no legal move to escape.

6. A tactic in chess intended to lure a defending piece away from a square, line, or diagonal it is guarding.

7. The four squares at the middle of a chessboard: d4, e4, d5, and e5.

8. A position in chess in which the player whose turn it is to move has no legal move, and is not in check.

9. A tactic in chess where a single piece simultaneously attacks two or more opponent pieces.

10. A chess piece that moves diagonally any number of vacant squares.

11. The most powerful chess piece that can move any number of vacant squares in any direction.

12. A file on the chessboard that has no pawns of either color, allowing rooks to have maximum mobility.

13. A situation in chess where a piece is unable to move because it would expose a more valuable piece to attack.

14. A pawn that has no friendly pawns on adjacent files. It can be easily targeted and blockaded.

15. The initial moves of a chess game where players develop their pieces and control the center of the board.

16. The most important chess piece that must be safeguarded throughout the game.