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

New Northwestern Medicine research published in Nature Communications suggests that a substance produced when gut bacteria digest dietary fiber may leave a durable molecular mark on cells lining the intestine.

From Science Daily ● Aug. 21, 2026

Therefore, it is “the default connectivity partner” for customers debating between copper and fiber components, in his view.

From MarketWatch ● Aug. 21, 2026

When Conagra’s vice president of culinary innovation Tom Frain first learned about growing adoption of GLP-1s, he envisioned being tasked with designing rabbit food made with kale and fiber supplements.

From The Wall Street Journal ● Aug. 19, 2026

Stuckey, the Mattson executive, fields requests from some of the country’s biggest food makers looking to miniaturize their products, or soup them up with protein or fiber.

From The Wall Street Journal ● Aug. 19, 2026

Native Americans of the eastern United States domesticated no locally available wild pulse, no fiber crop, no fruit or nut tree.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Scientists have also developed specialized optical fibers for technologies including fiber lasers, fiber endoscopes, and fiber sensors.

From Science Daily ● Aug. 22, 2026

This phenomenon, called Brillouin-Mandelstam scattering, is already known from conventional optical fibers.

From Science Daily ● Aug. 22, 2026

Its fibers were also better aligned, giving the new tissue a closer resemblance to natural, healthy bone.

From Science Daily ● Aug. 12, 2026

The company, one of the biggest makers of paper-based products in the world, is hopeful that hesperaloe could help them reach their ambition to eventually stop using fibers from natural forests.

From The Wall Street Journal ● Aug. 7, 2026

This one I also made of yucca fibers softened in water and braided into twine.

From "Island of the Blue Dolphins" by Scott O'Dell

Related Words

• grain
• thread
• tissue