1. Matrix - a rectangular arrangement of numbers into rows and columns
2. Entries - numbers inside the matrix
3. Dimension - the size of the matrix stated as the # of rows by the # of columns
4. Scalar - a number on the outside of the matrix, which indicates to multiply
5. Scalar Multiplication - multiply each entry of the matrix by the scalar (like the distributive property)

1. The matrices must be the same size.
2. If subtracting, add the opposite.
3. Add the numbers in the same position.
4. The answer will be the same size as those being added.