noun
nyctophobia; fear of the dark; scotophobia
Clinical term for an irrational fear of darkness. Used in medical or psychological contexts.
暗所恐怖症の人は、暗い部屋に一人でいるのが怖い。
People with nyctophobia are afraid of being alone in a dark room.
Compound of 暗所 (dark place) + 恐怖症 (phobia). A straightforward medical term.