Speed is a scalar quantity . It has only magnitude . | Velocity is a vector quantity . It has both magnitude and direction . The scalar absolute value (magnitude) of velocity is called "speed" .
When something moves in a circle and returns to its starting point, its average speed is circumference divided by time taken . | When something moves in a circle and returns to its starting point, its average velocity is zero .
Example : If a car is said to travel at 90 km/h, its speed has been specified. | If the car is said to move at 90 km/h to the sorthsouth, its velocity has now been specified.