Definition of Matrix
A matrix is an array of objects, usually numbers.
You used some in your work in Unit 2.
All of these are examples of matrices.
The first two are “square”, the first 2x2 and the
second 3x3. The third one is 3x2, the fourth one
a “row” matrix at 1x3, and the fifth one a
“column” matrix at 3x1.