The speed of an object plus its direction is called velocity.

Here's why:

* Speed is a scalar quantity, meaning it only has magnitude (how fast something is moving). For example, 50 mph.

* Direction is a crucial piece of information that tells us where the object is moving.

* Velocity combines both speed and direction. It's a vector quantity, meaning it has both magnitude and direction. For example, 50 mph east.

So, while speed tells us "how fast," velocity tells us "how fast and in what direction."