noun

• (countable) A single elongated piece of a given material, roughly round in cross-section, often twisted with other fibers to form thread.
• (uncountable) A material in the form of fibers.
• (textiles) A material whose length is at least 1000 times its width.
• Dietary fiber.
• (figuratively) Moral strength and resolve.
• (mathematics) The preimage of a given point in the range of a map.
• (category theory) The pullback of a morphism along a global element (called the fiber of the morphism over the global element).
• (computing) A kind of lightweight thread of execution.
• (cytology) A long tubular cell found in bodily tissue.