Fibre

Fibre (British spelling) or fiber (American spelling) is a term used for several classes of long, flexible strands derived from plants, animals, or synthetic processes. The word is common in nutrition, textiles, and telecommunications, where it has distinct meanings in each context.

Dietary fibre consists of plant-based carbohydrates and lignin that resist digestion in the small intestine. It is commonly classified as soluble or insoluble: soluble fibre forms a gel and can help regulate blood glucose and cholesterol, while insoluble fibre adds bulk to stool and aids bowel regularity. Major sources include fruits, vegetables, cereals, legumes, and seeds. Public health guidelines recommend higher fibre intakes, which are associated with various health benefits.

In textiles, a fibre is a raw material that can be spun into yarns and woven or knitted into fabrics. Natural fibres include cotton, wool, silk, and linen; regenerated fibres include viscose and lyocell; and synthetic fibres include nylon, polyester, and acrylic. Fibres differ in length, strength, elasticity, moisture absorption, and thermal properties, which influence fabric texture, durability, and care requirements.

Optical fibre is a thin strand of glass or plastic that transmits light with low loss over long distances by total internal reflection. It underpins modern telecommunications, enabling high-bandwidth data transmission, and is used in medical imaging and sensors. Fibres are classified as single-mode or multi-mode, and by core and cladding materials.