noun

keratin

KERR-uh-tin

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Keratin (noun) means a tough, fibrous protein that forms the main structural material of hair, nails and the outer layer of skin, and of horns, hooves and feathers in animals. Its strands pack together tightly, which is what makes these tissues hard and water-resistant. Example: “Nails are made largely of keratin.”

noun

A tough, fibrous protein that forms the main structural material of hair, nails and the outer layer of skin, and of horns, hooves and feathers in animals. Its strands pack together tightly, which is what makes these tissues hard and water-resistant.

"Nails are made largely of keratin."

"The biologist explained that a rhino's horn is keratin, the same protein as fingernails."

informal A hair treatment named after this protein, in which a product is applied and sealed with heat to make hair smoother and straighter for a period of weeks.

"She booked a keratin at the salon before the wedding."

How to use keratin

Learner’s notes

In plain EnglishThe tough protein that hair, nails and the outer skin are made of.

When to use it

Everyday in cosmetics and hairdressing; also standard biological vocabulary. The adjective is keratinous.

Memory tip

Do not confuse keratin with creatine, a completely unrelated compound associated with muscle and sports supplements.

Trace the full origin ↓

Easily confused with

collagen → carotene creatine → elastin

Common pairings

keratin treatment hydrolysed keratin keratin protein keratin-rich

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

Test yourself on “keratin” A quick quiz — meaning, synonyms & usage →

Fill the gap

Can you complete this real example?

Nails are made largely of _____.

Etymology

From Greek keras, meaning horn, plus the chemical suffix -in.

Origin: Greek

Synonyms

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fibrous protein structural protein keratin treatment Brazilian blowout ceratin

Rhymes for keratin

Latin satin gratin gelatin

See all rhymes for keratin →

Frequently asked questions

What is the difference between keratin and collagen?

Both are structural proteins, but they sit in different places and do different jobs. Keratin forms hair, nails and the outer skin layer; collagen forms the connective framework in the deeper layers of skin and in tendons, bones and cartilage.

Does keratin in a shampoo become part of the hair?

No. Hair keratin is built inside the follicle by living cells; the visible shaft is not alive and cannot incorporate new protein. Keratin listed on a product label refers to protein fragments that coat the hair surface.

What is a keratin treatment?

It is a salon service in which a solution is applied to hair and sealed in with a flat iron, leaving the hair smoother and less prone to frizz for several weeks. The name refers to the protein, though formulations vary widely between salons and brands.

What is the meaning of keratin?

"keratin" (noun) means a tough, fibrous protein that forms the main structural material of hair, nails and the outer layer of skin, and of horns, hooves and feathers in animals. Its strands pack together tightly, which is what makes these tissues hard and water-resistant.