Meaning

noun the time of day immediately following sunset

noun the diffused light from the sky when the sun is below the horizon but its rays are refracted by the atmosphere of the earth

noun a condition of decline following successes

originPIE word *dwóh₁ From Middle English twilight, twyelyghte, equivalent to twi- (“double, half-”) + light, literally ‘second light, half-light’. Cognate to Scots twa licht, twylicht, twielicht (“twilight”), Low German twilecht, twelecht (“twilight”), Dutch tweelicht (“twilight, dusk”), German Zwielicht (“twilight, dusk”). Compare Old English twēone lēoht (“twilight”).

Etymology from Wiktionary, CC BY-SA 3.0