Nyctophobia is a pathological fear of the dark. The word is formed from the Greek "nyx" (night) and the Greek "phobos" (fear). See -phobia. Another term for fear of the dark is scotophobia. From the Greek "skotos" (darkness) and –phobia.
Sufferers have an an abnormal and persistent dread of the dark and experience anxiety even though they may rationally understand that the dark does not pose such a great threat.