There are many quantities that require only a number to describe them. For example: What time is it? (9:00 A.M.) How far is Ganta from Monrovia? (201 miles) How fast did you drive the car? (80 km/h) How cold is it? (4°C) What is the area of the rectangle? (6 cm²) What is the cost of the ticket? (L $10.50) Such quantities as time, distance, speed, temperature, area and amount of money are described by their magnitudes. A quantity which is described by only magnitude is called scalar. In fact, the word scalar is usually used as a synonym for a number.

There are many other quantities that need a direction as well as a magnitude to describe them. For Example: Where is Ganta from Monrovia? (201 miles; Northeast) What force is acting on the car? (1200 lb; down). Such quantities as displacement and force that need a direction as well as magnitude to describe them are called vector quantities (or simply, vectors). The following are more examples of vectors.

Example

An airplane is flying at a speed of 500 km/hr in the direction of N45°E. This is a the velocity of the airplane Velocity is
speed and direction of a moving object. It is a vector.