Matrix (mathematics)
Matrices are often represented by capital roman letters such as ,  and , and there are rules for adding, subtracting and "multiplying" matrices together, but the rules are different than for numbers. As an example, the product  does not always give the same result as , which is the case for the multiplication of ordinary numbers. A matrix can have more than 2 dimensions, such as a 3D matrix. Also, a matrix can be one-dimensional, as a single row or a single column.