Meaning of “dark” - Learner’s Dictionary

dark

noun uk us /dɑːk/
the dark

B1 somewhere where there is no light:

I don't like going out alone in the dark.
He's scared of the dark.
before/after dark

B1 before/after it becomes night:

She doesn't let her children out after dark.

(Definition of “dark noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)