Here's a more formal definition:

Speed is the rate at which an object changes its position.

Key points about speed:

* It's a scalar quantity: It only tells us how fast something is moving, not in what direction.

* It's usually measured in units like: meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph).

* It can be constant or changing: A car traveling at a steady 60 mph has a constant speed, while a rollercoaster has a changing speed.

Let me know if you'd like to explore related concepts like velocity or acceleration!