In Mathematics, you learned that a number is something that represents a quantity. For example if you have 5 books, 6 apples and 1 bicycle, the 5, 6, and 1 represent how many of each item you have.

These kinds of numbers are known as *scalars*.

- Definition 1: Scalar
A scalar is a quantity that has only magnitude (size).

An extension to a scalar is a vector, which is a scalar with a direction. For example, if you travel 1 km down Main Road to school, the quantity **1 km down Main Road** is a vector. The “**1 km**” is the quantity (or scalar) and the “**down Main Road**” gives a direction.

In Physics we use the word *magnitude* to refer to the scalar part of the vector.

- Definition 2: Vectors
A vector is a quantity that has both magnitude and direction.

A vector should tell you **how much** and **which way**.

For example, a man is driving his car east along a freeway at 100km·h-1100km·h-1. What we have given here is a vector – the velocity. The car is moving at 100km·h-1100km·h-1 (this is the magnitude) and we know where it is going – east (this is the direction). Thus, we know the speed and direction of the car. These two quantities, a magnitude and a direction, form a vector we call velocity.