ETYM Cf. French phosphorescence.
Light without heat, continuing after exposure to radiation which causes it; faint glow in dark without apparent cause.
In physics, the emission of light by certain substances after they have absorbed energy, whether from visible light, other electromagnetic radiation such as ultraviolet rays or X-rays, or cathode rays (a beam of electrons). When the stimulating energy is removed phosphorescence ceases, although it may persist for a short time after (unlike fluorescence, which stops immediately).
A fluorescence that persists after the bombarding radiation has ceased.