Definition:Matrix/Diagonal Elements

Definition
Let $\mathbf A = \sqbrk a_{m n}$ be a matrix.

The elements $a_{j j}: j \in \closedint 1 {\min \set {m, n} }$ constitute the main diagonal of the matrix.

The elements themselves are called the diagonal elements.

Also defined as
Some sources define the diagonal elements only for a square matrix.

Also known as
Some sources refer to diagonal entries.

The main diagonal is also known as the principal diagonal and the leading diagonal.

Also see

 * Definition:Upper Triangular Element
 * Definition:Lower Triangular Element