a very fine thread or threadlike structure; a fiber or fibril

filaments of gold.

a single fibril of natural or synthetic textile fiber, of indefinite length, sometimes several miles long.

a long slender cell or series of attached cells, as in some algae and fungi.

Botany . the stalklike portion of a stamen, supporting the anther.

Ornithology . the barb of a down feather.

(in a light bulb or other incandescent lamp) the threadlike conductor, often of tungsten, in the bulb that is heated to incandescence by the passage of current.

Electronics . the heating element (sometimes also acting as a cathode) of a vacuum tube, resembling the filament in an incandescent bulb.

Astronomy . a solar prominence, as viewed within the sun's limb.

noun

fiber , fibril , hair , stalk , strand , tendril , thread , wire