We have already encountered matrices with one row or one column. A matrix is a collection of numbers ordered by rows and columns. In this chapter, we will typically assume that our matrices contain only numbers. The above sentence is abbreviated as det ab cd adcb. It is customary to enclose the elements of a matrix in parentheses, brackets, or braces. Matrices a matrix is basically an organized box or array of numbers or other expressions. The numbers n and m are called the dimensions of the matrix.
A vector of dimension n can be viewed either as a 1. In order to make sense, both of the matrices in the sum or difference must have the same number of rows and columns. It makes no sense, for example, to add a y ij\ matrix to a w ij\ matrix. The mathematical concept of a matrix refers to a set of numbers, variables or functions ordered in rows and columns.