Nighttime and Pitch-dark

Nighttime noun - The time from sunset to sunrise when there is no visible sunlight.

Pitch-dark and nighttime are semantically related. In some cases you can replace phrase "Pitch-dark" with "Nighttime", this terms are similar.

Pitch-dark adjective - Being without light or without much light.

Nighttime and pitch-dark are semantically related. Sometimes you can use "Nighttime" instead a noun phrase "Pitch-dark".