A Set of numbers aij (called elements) arranged in a rectangular array of m rows and n columns constitutes a matrix of orders m × n. For example, of the arrays

the first is a matrix of two rows and three columns, i.e. of orders 2 × 3, the second is a square matrix of orders 3 × 3.

From a square matrix of orders n × n we can form a determinant of order n. Thus from the above square matrix we can form the determinant of order 3