A mass of gas suspended over the chromosphere by magnetic fields and seen as dark ribbons threaded over the solar disk. A filament on the limb of the Sun seen in emission against the dark sky is calle
d a prominence.
If a solar prominence occurs on the disc of the sun it appears darker than its background (due to the lower temperature of the plasma). These are referred to as solar filaments.
A type of nebula, generally ionized, consisting of filament-like structures of gas, such as the Veil Nebula (NGC 6960) or the supernova remnant IC 443.
A broad pattern of fibrils in the chromosphere, marking a portion of a magnetic polarity inversion line where a filament may soon form or where a filament recently disappeared. Filament channels are
frequently observed in soft x-rays images as dark lanes.