n.1 a slender threadlike body or fibre (esp. in animal or vegetable structures).
2 a conducting wire or thread with a high melting-point in an electric bulb or thermionic valve, heated or made incandescent by an electric current.
3 Bot. the part of the stamen that supports the anther.
4 archaic (of air, light, etc.) a notional train of particles following each other.
Derivatives:
filamentary adj. filamented adj. filamentous adj.
Etymology: F filament or mod.L filamentum f. LL filare spin f. L filum thread