means The property of a substance to keep glowing softly for a while after the light hitting it has been switched off — a delayed, lingering luminescence, unlike the instant flash of fluorescence.

from Built from Greek 'phōsphoros,' the 'light-bearer' — 'phōs' (light) plus 'pherein' (to carry) — the same name the Greeks gave the morning star, Venus. The element phosphorus borrowed that name in the 17th century because it glowed eerily in the dark, and 'phosphorescence' followed as the word for that very glow, with the noun-ending '-escence' marking it as an ongoing state of becoming light.