Define a matrix
An ordered array of numbers such as
Is called a matrix. The numbers are called elements of the matrix. Matrices (the plural of matrix) are named according to the number of rows and columns they contain. The rows are read horizontally, and the columns are read vertically.
For example, the first row in the preceding matrix is 2 3 4 and the first column is 
. This matrix is a 2 3 3 (read “two by three”) matrix because it has 2 rows and 3 columns. The number of rows is given first, and then the number of columns.