Matrix element

A matrix element is a number or a mathematical expression that occupies a single position in a rectangular array of numbers and expressions that, in its entirety, is called a matrix. Often, a matrix element is denoted by a symbol that stands for the entire matrix, followed by the row and column numbers displayed as subscripts, for example A_i,j or just A_ij for the element in the i^th row and j^th column of the matrix A.

Another usage is for a mathematical object which is called a matrix coefficient, unambiguously.