3×3

3×3, read as “three by three,” is a common notation for describing dimensions that are three units wide and three units tall. It is also used to denote the arithmetic product of 3 and 3, which equals 9. The symbol × is used to indicate multiplication or cross-dimensional relationships.

3×3 matrices are square arrays with three rows and three columns. In linear algebra they represent linear transformations in three-dimensional space, and their key properties include determinant, invertibility, and eigenvalues. A 3×3 matrix can encode systems of three linear equations and their solutions.

3×3 grids appear in games and puzzles. The classic tic-tac-toe game is played on a 3×3 board, where two players compete to form a straight line. In Sudoku, the full grid is 9×9 and is partitioned into nine 3×3 subgrids, each consisting of three by three cells.

3×3 also features in sports formats. FIBA 3×3 is a form of basketball played on a half-court with three players per side; it emphasizes speed and spacing and has hosted international competitions and Olympic events since 2010s. In other contexts, 3×3 can describe small-scale layouts, microstructures, or design grids where a uniform three-by-three arrangement is relevant.