Here's why:

* Velocity is a vector quantity. This means it has both magnitude (size) and direction.

* Magnitude: The magnitude of velocity is the speed, which is measured in units like meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph).

* Direction: This tells you which way the object is moving. For example, "5 meters per second north" or "20 km/h towards the east."

Example:

Imagine two cars moving at the same speed of 60 km/h. One is traveling north, and the other is traveling south. Although they have the same speed, they have different velocities because their directions are opposite.

In summary: You need both a numerical value (speed) and a direction to describe velocity accurately.