1a slender thread-like object or fibre, especially one found in animal or plant structures:each myosin filament is usually surrounded by 12 actin filaments
Botany the slender part of a stamen that supports the anther.
Astronomy a narrow streamer from the sun’s chromosphere or in its corona.
2a conducting wire or thread with a high melting point, forming part of an electric bulb or thermionic valve and heated or made incandescent by an electric current.