keratin

/ˈkɛrətən/

Keratin is the name of the protein that forms your hair and fingernails. You've got something in common with spiders, too — their silk is also made from keratin.

Keratin is a hard, fibrous protein that gives structure to certain body parts in humans and animals. Your toenails are made up of keratin, and so are your cat's claws. Horns, nails, hair, feathers, shells, and beaks — all of these are composed of keratin. The word comes from the Proto-Indo-European root ker, meaning "horn," followed by the scientific suffix -in, denoting a chemical.

Definitions of keratin

1. noun

   a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair, feathers, nails, and hooves
   synonyms: ceratin

   type of:

   albuminoid, scleroprotein

   a simple protein found in horny and cartilaginous tissues and in the lens of the eye