noun The soft light in the sky seen before the rising and (especially) after the setting of the sun, occasioned by the illumination of the earth’s atmosphere by the direct rays of the sun and their reflection on the earth.
I could just make out her face in the twilight.
noun The time when said light is visible; the period between daylight and darkness.
It was twilight by the time I got back home.
noun Any faint light through which something is seen.
noun The time when the sun is less than 18° below the horizon.
noun An in-between or fading condition through which something is perceived.
The twilight of one's life
adjective Pertaining to or resembling twilight; faintly illuminated; obscure.
adjective Synonym of mesopelagic (“Describing the pelagic zone of the ocean between the photic epipelagic and the aphotic bathypelagic zones, characterized by very minimal light.”)