filament

A filament is a slender, threadlike structure that is longer than it is wide. The term is used across many disciplines to describe thin, elongated strands in living organisms, materials, and the cosmos.

In biology, filaments are key components of the cytoskeleton. Actin filaments (microfilaments), intermediate filaments, and microtubules provide shape, enable movement, organize organelles, and drive processes such as cell division. Filaments form networks and, in muscles, actin filaments interact with myosin to produce contraction.

In textiles, a filament refers to a continuous strand of material used to form filament yarns. These can be natural, such as silk, or synthetic, such as polyester, nylon, or acrylic. Filament yarns are typically smooth and lustrous, in contrast to yarns spun from short fibers (staple fibers).

In botany, the filament is the stalk of a flower’s stamen that supports the anther and releases pollen.

In technology and industry, a filament can be a heated wire that emits light, most famously the tungsten filament in incandescent lamps. In 3D printing, filament denotes the plastic feedstock, usually a spool of PLA, ABS, or PETG, with common diameters of 1.75 or 2.85 mm.

In astronomy, cosmic filaments are enormous, threadlike structures that form the cosmic web, linking galaxy clusters through filaments of dark matter and galaxies over vast distances.