A matrix is a group of numbers arranged by rows and columns. There must be at least one row and one column They are usually named by a symbol, say the uppercase Latin letter A, and in that form enter into expressions and equations like

C = A + B

which would indicate that I have added the two matrices A and B together to give a result called the C matrix. We will look at operations upon matrices like this addition later, but note for the moment that the notation implies that we represent all of the numbers within a matrix at once by using a single symbol.

We normally say that a matrix contains elements, a term which you may be familiar with from set theory. But a matrix is more than just a simple set as it has an internal arrangement of positions to place the elements. Plus there are specific rules for matrices from other matrices, we call these matrix operations.