A matrix (plural matrices) is a rectangular array of numbers. Matrices are organized into rows of columns and each number in a matrix is commonly referred to as an entry, term, or element. Below is an example of a 2 × 2, read 2 by 2, matrix.

In this matrix, a, b, c, and d, are variables representing the entries of the matrix, A. Matrices can undergo operations such as multiplication, addition, and subtraction, among others, but not necessarily in ways that are exactly analogous to their arithmetic operations. They can also be used to represent linear systems of equations and to solve said systems. Refer to the matrix notation page for more information on the notation used with matrices as well as some basics of matrices, or explore the other pages for further detail.