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

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Etymology

Origin of fiber

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

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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

While chip maker Marvell specializes in networking and switches, Lumentum specializes in fiber optics.

From MarketWatch ● Nov. 2, 2026

New research reveals why aging muscles shift toward a different type of muscle fiber and identifies a crucial molecule that could offer a new approach to treating muscle loss.

From Science Daily ● Oct. 28, 2026

The supplement tested in the study was inulin, a naturally occurring fiber found in foods such as chicory root, Jerusalem artichokes, and certain other vegetables.

From Science Daily ● Oct. 28, 2026

“Based on the demand we are seeing, we expect both our fiber and edge computing to add meaningfully to our future growth,” he says.

From The Wall Street Journal ● Oct. 27, 2026

“Maybe collect hair and fiber samples like they do on TV.”

From "The Smartest Kid in the Universe" by Chris Grabenstein

Fast-twitch fibers produce powerful, rapid movements but fatigue relatively quickly.

From Science Daily ● Oct. 28, 2026

Surprisingly, aging muscles also develop a greater proportion of slow-twitch fibers, even though these fibers depend heavily on the very mitochondria that are losing their ability to function.

From Science Daily ● Oct. 28, 2026

Their muscles also developed more fibers with a high capacity for using oxygen, helping improve physical endurance.

From Science Daily ● Oct. 24, 2026

The chronic condition occurs when the immune system attacks the protective layer of nerve fibers.

From The Wall Street Journal ● Oct. 23, 2026

I feel it wrapping around me, entwining me in sharp fibers.

From "Catching Fire" by Suzanne Collins

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Related Words

• grain
• thread
• tissue

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