The speed of an object in the direction it moves is called its velocity.

Here's why:

* Speed is how fast an object is moving, regardless of direction. It's a scalar quantity, meaning it only has magnitude (e.g., 10 meters per second).

* Velocity is how fast an object is moving *and* in what direction. It's a vector quantity, meaning it has both magnitude and direction (e.g., 10 meters per second *eastward*).

So, if you want to know how fast an object is moving in the direction it's traveling, you need to consider its velocity.