keratin

noun

ker·​a·​tin ˈker-ə-tən How to pronounce keratin (audio)
: 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 adjective

Examples of keratin in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Remington Shine Therapy 2-Inch Hair Straightener Iron Buy Now on Amazon This hair straightener has advanced ceramic plates for a superior styling experience, and it’s infused with argan oil, keratin and a micro-conditioner to leave your hair super silky and shiny. Lauryn Jiles, Miami Herald, 3 Mar. 2025 This drugstore gem is made with hydrolyzed keratin and pea protein to help support hair strength, while botanical extracts like chia seed oil and algae maintain softness and shine. Siena Gagliano, Allure, 1 Mar. 2025 The cortex, in the center, is also made of keratin, but is more flexible because it is not calcified. Marie Bladt, Vogue, 28 Feb. 2025 The powder's keratin fibers attach to your hair to help build and strengthen strands, lending a look of fullness and volume, especially when used over time. Deanna Pai, Allure, 21 Feb. 2025 See All Example Sentences for keratin

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

Time Traveler
The first known use of keratin was circa 1849

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Cite this Entry

“Keratin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keratin. Accessed 12 Mar. 2025.

Kids Definition

keratin

noun
ker·​a·​tin ˈker-ət-ᵊn How to pronounce keratin (audio)
: a sulfur-containing protein that makes up hair and horny tissues (as nails)

Medical Definition

keratin

noun
ker·​a·​tin ˈker-ət-ən How to pronounce keratin (audio)
: 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

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