By the definition of scalar quantity, they only have a magnitude and no definite direction. Speed here does not have any specific direction and have only magnitude so is a scalar quantity.

Why speed is a scalar quantity and velocity is vector quantity?

Velocity has both magnitude and direction that is why it is a vector quantity. Whereas, Speed has only magnitude and no direction that is why it is a scalar quantity.

Is speed an example of scalar quantity?

Speed is a scalar quantity – it is the rate of change in the distance travelled by an object, while velocity is a vector quantity – it is the speed of an object in a particular direction.