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
Maryanne VollersWool fibers are composed of keratin proteins bundled into microfibrils.—A. Goho
compare keratinocyte
A. GohoExamples of keratin in a Sentence
Recent Examples on the Web
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
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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
Cite this Entry
“Keratin.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/keratin. Accessed 12 Mar. 2025.
Copy CitationKids 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
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