keratin

noun

ker·​a·​tin ˈker-ə-tən 

: any of various sulfur-containing, fibrous, acidic or basic proteins chiefly of epithelial cells and tissues that are relatively insoluble and resistant to degradation, form filaments which assemble into bundles to provide structural support, and are the primary component of hair, nails, horns, claws, hooves, quills, scales, feathers and the epidermal layer of skin

Note: In addition to its structural properties, keratin also plays a role in cell growth and proliferation, cellular transport of substances, and intercellular communication.

Rhino horn is not actually horn but densely compacted fibers of keratin, a protein found in hair and fingernails.

—Maryanne Vollers

Wool fibers are composed of keratin proteins bundled into microfibrils.

—A. Goho

compare keratinocyte

keratinous

kə-ˈra-tə-nəs 

adjective

Examples of keratin in a Sentence

Recent Examples on the Web

Now, about that ashwagandha: Though the ingredient is thought to help stimulate keratin production and is commonly used in hair potions promising thicker, stronger, healthier hair, Nutrafol’s version of the adaptogen is a bit different. —Jenny Berg, Allure, 23 Oct. 2024

This innovative product is like a bond builder for your nails, and is formulated with a patented Ulti-Plex Technology that helps repair and build keratin bonds for stronger, healthier nails. —Karina Hoshikawa, refinery29.com, 17 Sep. 2024

Schwarzkopf Keratin Blonde Anti-Brass Purple Mask $12 at Amazon In addition to eliminating yellow tones, this violet treatment contains keratin to keep strands strong. —Jackie Fields, Peoplemag, 11 Sep. 2024

The formulas include active ingredients such as bioactive keratin ferment, honey and protein known to strengthen the hair, reduce breakage, and promote a smoother and shinier appearance. —Anaja I. Smith, The Hollywood Reporter, 21 Oct. 2024

Word History

Etymology

borrowed from German Keratin, from Greek kerat-, stem of kéras "horn" + German -in -in entry 1 — more at kerato-

Note: The term was introduced by the German physician and chemist Johann Franz Simon (1807-43) in Handbuch der angewandten medizinischen Chemie, 1. Theil, Medizinisch-analytische Chemie (Berlin, 1840), p. 49.

First Known Use

circa 1849, in the meaning defined above

Kids Definition

keratin

noun

ker·​a·​tin ˈker-ət-ᵊn 

: a sulfur-containing protein that makes up hair and horny tissues (as nails)

Medical Definition

keratin

noun

ker·​a·​tin ˈker-ət-ən 

: any of various sulfur-containing fibrous proteins that form the chemical basis of horny epidermal tissues (as hair and nails) and are typically not digested by enzymes of the gastrointestinal tract see pseudokeratin