(a) a shadowy region; (b) a world characterized by uncertainty, obscurity, or decline; (c) the world which comes to life after sunset…

In phrases denoting an evening spent socializing or at leisure. night out: (originally) the evening on which a domestic servant was free to go out…

The social activities or entertainment available at night, usually in a town or a city; (also, occasionally) people or animals active at night.

The practice or activity of going to nightclubs.

The range of entertainment and social activities available in a place at night; nightlife.