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

But she said that faster growth had occurred in offerings geared toward international cuisine, fiber and protein, smaller package sizes and bigger family-sized packs.

From MarketWatch ● Oct. 2, 2026

The average AT&T fiber household now uses more than one terabyte of data each month, up fivefold from a decade ago, the companies said Tuesday.

From The Wall Street Journal ● Sep. 29, 2026

Corning announces a multibillion-dollar partnership to supply AT&T with fiber and cable for high-speed internet.

From Barron's ● Sep. 29, 2026

The company has tried to roll out new products — like Doritos with protein and Pepsi with fiber — to hold shoppers’ interest.

From MarketWatch ● Sep. 28, 2026

I took my skirt of yucca fiber, however, for I had spent many days making it and it was very pretty, and also my otter cape.

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

He points to research estimating the environmental impact of cellulosic microfibers as one to two orders of magnitude lower than that of synthetic fibers, largely because they degrade faster.

From The Wall Street Journal ● Sep. 24, 2026

But while natural fibers in many cases may use fewer chemicals than synthetics, a body of research is challenging whether they deserve a free pass.

From The Wall Street Journal ● Sep. 24, 2026

Rather than replacing lost muscle or neurons, the approach is aimed at making existing muscle fibers more responsive to the messages they receive.

From Science Daily ● Sep. 24, 2026

Eventually, MS can cause permanent damage to the nerve fibers, and symptoms vary from person to person, depending on the location and severity of the damage in the nervous system.

From Los Angeles Times ● Sep. 22, 2026

Harry could feel her digging at the rope’s tough fibers to work the knots free.

From "Harry Potter and the Deathly Hallows" by J.K. Rowling

Related Words

• grain
• thread
• tissue