What does "keratin" mean?

The protein of which hair and nails are composed.

Keratin

Common synonyms include: ceratin, fibrous protein, intermediate filament protein, keratin protein family, structural protein.

/ˈkɛrətɪn/ noun

noun ·Rare ·Advanced level

Noun

1
The protein of which hair and nails are composed. countable, uncountable
2
a fibrous scleroprotein that occurs in the outer layer of the skin and in horny tissues such as hair, feathers, nails, and hooves wordnet

"Keratin is one of a family of fibrous structural proteins known as scleroproteins."

Borrowed from German Keratin, from Ancient Greek κέρας (kéras, “horn”) + -in.