fiber

American  

[fahy-ber] / ˈfaɪ bər /

especially British, fibre

noun

• fibers
  plural

1. a fine, threadlike piece, as of cotton, jute, or asbestos.

2. a slender filament.

   a fiber of platinum.

3. filaments collectively.

4. matter or material composed of filaments.

   a plastic fiber.

5. something resembling a filament.

6. an essential character, quality, or strength.

   people of strong moral fiber.

7. Botany.

   1. filamentous matter from the bast tissue or other parts of plants, used for industrial purposes.

   2. a slender, threadlike root of a plant.

   3. a slender, tapered cell which, with like cells, serves to strengthen tissue.

8. Anatomy, Zoology. a slender, threadlike element or cell, as of nerve, muscle, or connective tissue.

9. Also called bulk, dietary fiber, roughage.  Nutrition.

   1. the structural part of plants and plant products that consists of carbohydrates, as cellulose and pectin, that are wholly or partially indigestible and when eaten stimulate peristalsis in the intestine.

   2. food containing a high amount of such carbohydrates, as whole grains, fruits, and vegetables.

10. Chemistry. vulcanized fiber.

11. Optics. optical fiber.

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fiber British  

/ ˈfaɪbə /

noun

1. the usual US spelling of fibre

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fiber Scientific  

/ fī′bər /

1. The parts of grains, fruits, and vegetables that contain cellulose and are not digested by the body. Fiber helps the intestines absorb water, which increases the bulk of the stool and causes it to move more quickly through the colon.

2. One of the elongated, thick-walled cells, often occurring in bundles, that give strength and support to tissue in vascular plants. Fibers are one type of sclerenchyma cell.

3. Any of the elongated cells of skeletal or cardiac muscle, made up of slender threadlike structures called myofibrils.

4. The axon of a neuron.

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Other Word Forms

Derived Forms

• fiberless
  adjective
• interfiber
  adjective

Inflected Forms

Nouns

• fibers
  plural

Etymology

Origin of fiber

1350–1400; 1970–75 fiber for def. 9; Middle English fibre (< Middle French ) < Latin fibra filament

Explanation

Almost all fabrics, muscle structures, and even vegetables are composed of some sort of fiber, the noun meaning a long, thread-like substance. The word fiber is sometimes associated with moral character in a similar way that it is related to the physical material. The moral fiber of a person might be the thing that weaves together their character to make them the ethical (or unethical) person they are. For example, you might guess that the televangelist who asks for money from the elderly poor, but has a fancy sports car for every day of the week lacks moral fiber.

Example Sentences

See Examples For:

fiber fibers

Executives at other branded-goods companies in recent months have talked up their newest concepts: silk diapers, Doritos with protein, Pepsi with fiber, Capri Sun with electrolytes and “hydrating” hot chocolate.

From MarketWatch ● Sep. 16, 2026

Much of the internet already relies on light to carry information through fiber optic cables.

From Science Daily ● Sep. 11, 2026

Those subsidized tree farms are maturing now, unfortunately at a time when demand for wood fiber has been significantly reduced by global competition, increased use of recycled materials and other factors.

From The Wall Street Journal ● Sep. 4, 2026

"A lot of the fiber is taken off" in the industrial process, said Danielle Nierenberg, president of the not-for-profit Food Tank which seeks to build sustainable and equitable food systems.

From Barron's ● Sep. 3, 2026

“They’ve laid so much fiber in the ground that they’ve basically commoditized themselves. They are going to get into massive price wars with everyone and it’s going to be a disaster.”

From "The World Is Flat" by Thomas L. Friedman

When asbestos fibers are inhaled, they can become trapped in the lungs, where they trigger chronic inflammation that may eventually lead to cancer decades later.

From Science Daily ● Sep. 17, 2026

Natural fibers like cotton, cashmere and silk feature prominently in its clothes, a departure from other midmarket retailers that have turned to cheaper synthetics.

From The Wall Street Journal ● Sep. 10, 2026

Their brightness comes from light scattering off the exposed fibers of the traditional washi paper.

From Science Daily ● Sep. 10, 2026

These wire-like fibers eventually form connections with specific cortical neurons.

From Science Daily ● Sep. 4, 2026

“I could, uh, press the fibers under and sew them down. Or how about cutting the fibers off?”

From "The Woman Warrior" by Maxine Hong Kingston

Related Words

• grain
• thread
• tissue