What does the root word kerat mean from keratin?

The root word "kerat" in "keratin" comes from the Greek word "κέρας" (keras), which means "horn".

This makes sense because keratin is a fibrous protein found in many structures in animals, including:

* Horns: Keratin is the primary component of horns, hooves, and claws.

* Hair and nails: Keratin is also the main building block of hair and nails.

* Skin: Keratin is found in the outer layer of skin, providing protection and waterproofing.

So, "kerat" in "keratin" basically indicates that it's a material related to horn-like structures.