例

A matrix is a rectangular arrangement or array of elements. The dimensions of a matrix, ${\displaystyle m\times n}$, identify how many rows and columns a matrix has. ${\displaystyle m}$ represents the number of rows and ${\displaystyle n}$ represents the number of columns. Assuming that the matrix name is ${\displaystyle A}$, the matrix dimensions are written as ${\displaystyle A_{m\times n}}$.

The number of rows is ${\displaystyle 3}$.

The number of columns is ${\displaystyle 3}$.