Dimensions of a Matrix

This dimension is called an Identity Matrix.   It serves as the multiplicative identity. 

The numbers of rows and columns are the dimensions.The dimensions of a matrix refer to the number of rows and columns.The rows are the numbers going horizontal.The columns are the numbers vertical.When stating the dimension, the correct form would be the number of rows multiplied by the number of columns.

This matrix is one row by three columns or 1 x 3 matrix.

    This matrix is three rows by three columns or 3 x 3 matrix.

This matrix is three rows by two columns, so it is a 3 x 2 matrix.