5×5

5×5 denotes a two-dimensional size in which five units occur along each of two perpendicular directions, equivalently the product of 5 and 5, which equals 25. The notation is used in mathematics, computer science, and design to describe a square of elements arranged in five rows and five columns.

In linear algebra a 5×5 matrix consists of five rows and five columns and contains 25 entries. Such matrices can represent linear transformations in five-dimensional space or be used in numerical computations and data representations. Indexing typically uses row and column indices (i, j).

The term is also used in cryptography as the Polybius square, a five-by-five grid used to encode letters as coordinate pairs. Traditionally I and J share a cell, yielding 25 cells to map 26 letters.

Five-by-five grids appear in display technology, notably 5×5 LED dot matrices used in digital clocks, indicators, and simple signs.

In puzzles and games, 5×5 boards are common for variants of tic-tac-toe or five-in-a-row challenges, and word searches or magic squares may use 5×5 layouts.

In computer vision and image processing, a 5×5 kernel or filter is a small matrix used for convolution to detect edges or blur images.