Here's why:

* Speed is a scalar quantity, meaning it only has magnitude (how fast something is moving).

* Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

Example:

* A car traveling at 60 mph has a speed of 60 mph.

* A car traveling at 60 mph north has a velocity of 60 mph north.

In summary: Velocity is a vector quantity because it includes both speed and direction.