# fiber /ˈfaɪbɝ/ (US) Source: https://englishreference.com/word/fiber Updated: 2026-08-15 ## Senses ### 1. a single thread noun · CEFR B2 · American English a single thin thread of a material like cotton, wool, or nylon. For teachers: a single elongated piece of material, typically cylindrical, which can be spun into yarn or thread. - The detective found a tiny blue fiber from a sweater on the rug. - Forensic analysts identified a synthetic fiber caught in the door frame that matched the specific blend used in the suspect's jacket. Usage: Countable in this sense. ### 2. dietary roughage noun · CEFR B2 · American English the part of food, like vegetables and grains, that helps your body digest. For teachers: indigestible carbohydrate derived from plants that aids in the passage of food through the digestive system. - You should eat more fruit and beans to get enough fiber in your diet. - Nutritionists recommend a high-fiber diet to maintain gut health and reduce the risk of chronic metabolic diseases. Usage: Usually uncountable when referring to the nutrient. ### 3. biological tissue noun · CEFR C1 · American English · Technical a long, thin cell in your body, such as in a muscle or nerve. For teachers: an elongated, threadlike structure or cell found in animal or plant tissue. - The athlete suffered a tear in a muscle fiber during the race. - Microscopic examination revealed that the nerve fibers were beginning to regenerate after the surgical intervention. ### 4. moral character noun · CEFR C2 · American English · Literary the inner strength or character that makes a person do the right thing. For teachers: the essential character, nature, or moral strength of a person. - Hard work and honesty were part of his moral fiber. - The crisis tested the very fiber of her being, forcing her to choose between personal gain and ethical duty. Teaching tip: Often used in the fixed phrase 'moral fiber'. ### 5. computing thread noun · CEFR C2 · American English · Technical a very light type of task that a computer program runs. For teachers: a particularly lightweight thread of execution that uses cooperative rather than preemptive multitasking. - The programmer used a fiber to manage the background tasks efficiently. - By implementing fibers instead of standard system threads, the application achieved higher concurrency with significantly lower memory overhead. ### 6. mathematical mapping noun · CEFR C2 · American English · Technical a set of points that all map to the same result in a math function. For teachers: the preimage of a single point under a given mapping or function. - We need to calculate the fiber of the function at this specific point. - In algebraic geometry, the fiber of a morphism over a point provides crucial information about the structure of the map. ## Examples - Whole grains are a great source of fiber. - The technician replaced the old copper wires with high-speed fiber to improve the office internet connection. - Modern textile manufacturing relies on a blend of natural cotton fiber and synthetic polymers to create fabrics that are both breathable and durable. --- From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.