Time after twilight and before night

One word substitute is Dusk.

Evening: the period of time at the end of the day, usually from about 6 p.m. to bedtime.
Dawn: the first appearance of light in the sky before sunrise.
Dusk: the darker stage of twilight.
Eclipse: an obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of illumination.