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

The Oribe Signature Complex, a combination of watermelon, lychee, and edelweiss flowers, works to defend hair follicles from the deterioration of natural keratin, keeping the hair shaft stronger and more resilient. —Carrie Honaker, Southern Living, 24 June 2024

The brick-and-mortar foray comes on the heels of Virtue’s launch of its Damage Reverse Serum, a leave-in treatment featuring the brand’s highest concentration of its proprietary alpha keratin 60ku protein. —Noor Lobad, WWD, 18 June 2024

Rubel suggests looking for beneficial ingredients such as amino acids and hyaluronic acid to help boost and retain moisture, as well as keratin for smoother and shinier cuticles, plus vitamins and conditioning agents for softer, stronger, and more hydrated locks. —Sophie Dodd, Peoplemag, 7 June 2024

It’s formulated with strand-protecting keratin and has a floral gardenia scent that could totally pass as perfume. —Sanah Faroke, Travel + Leisure, 15 May 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