Here's why:

* Cumulus comes from the Latin word "cumulus," meaning "heap" or "pile." This describes their appearance – fluffy, cotton-like heaps in the sky.

* Rising air: Cumulus clouds form when warm, moist air rises. As the air rises, it cools and the water vapor condenses into tiny water droplets, creating the cloud.

* Vertical growth: The rising air within the cloud continues to create more condensation, causing the cloud to grow vertically.

There are different types of cumulus clouds, such as:

* Fair-weather cumulus: These are small, puffy clouds that often indicate good weather.

* Cumulus congestus: These are larger, taller cumulus clouds that can develop into thunderstorms.

Let me know if you'd like to learn more about different types of clouds!