CHAPTER 01.05: INTRODUCTION: What is a square matrix?   In this segment we will talk about a square matrix. So we already know what a rectangular matrix is,   so let’s suppose we have a matrix that has M rows and N columns. Now, one will have the same number of rows as the same number of columns - like an N by N matrix. That is called a square matrix. The definition of a square matrix is: if the number of rows M, is same as the number of columns N for a  matrix that is by the order N by N then A is a square matrix.   So let’s look at an example. Somebody gives me a matrix which looks like this: 20, -3, 6, 7, 4, 2, -1, 3, and 7.2. So, in this case you are finding out that it has 3 rows - 1, 2, 3 - and it has 3 columns. It is a 3 by 3 matrix. So you are finding out that the number of rows is the same as the number of columns. What that means is that it is a square matrix; because the number of rows are the same as the number of columns, in this case being the number 3. And that is the end of this segment.