Here's why:

* Cloud Classification: Clouds are classified based on their altitude and shape.

* Middle-Level Clouds: Clouds that form between 2,000 and 7,000 meters (6,500 and 23,000 feet) are considered middle-level clouds.

* Alto Prefix: The prefix "alto" is used to indicate middle-level clouds.

Examples of middle-level clouds:

* Altostratus: Sheet-like, gray or bluish clouds that often cover the entire sky.

* Altocumulus: White or gray patches of clouds arranged in rounded masses or sheets.

* Altocumulus lenticularis: Lens-shaped clouds often found in mountainous areas.

Let me know if you have any other cloud-related questions!