Nyctophobia (from Greek νυκτ?? - nyktos, genitive of ν?ξ - nyx, "night")ν?ξ, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus and φ?βο? - phovos, "fear"φ?βο?, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus is a phobia characterized by a severe fear of the darkness. It is triggered by the brain’s disfigured perception of what would or could happen when in a dark environment.