Here's why:

* Speed describes the magnitude of movement. It tells you how quickly something is changing position, but doesn't tell you where it's going.

* Velocity describes both magnitude and direction. It combines speed with the direction of movement.

Think of these examples:

* Scenario 1: A car driving 60 miles per hour. This describes the car's speed. We don't know if it's going north, south, east, or west.

* Scenario 2: A car driving 60 miles per hour north. This describes the car's velocity. We now know both how fast it's moving and in what direction.

In summary:

* Speed is a scalar quantity (only magnitude).

* Velocity is a vector quantity (magnitude and direction).

Therefore, speed is an essential component of velocity, as it provides the information about the rate of movement.