The preceding chapter defined all the possible mathematical operations for vectors. This chapter defines a matrix and then revisits all those operations in terms of matrices. You'll find in Chapter 6, “Transformations,” that matrices can be used to move 2D objects around on the screen and manipulate 3D objects within the world coordinate system. Before you can use matrices, we have to address how they operate. If you're comfortable with vector operations, that will serve as a helpful foundation for learning matrix operations.