When people sleep, they somwetimes do have dreams. Very few peole can remember what their dreams were last night. Some people have good dreams, and other people have bad dreams. A bad dream is caled a nightmare.

If you look at where the word nightmare comes from, it means something like 'story of the night'. However, in old times (and even now) some people are afraid of the night. Thats how a story of the night became a 'nightmare'.

Albtraum | Nightmare | Pesadilla | Koŝmaro | Cauchemar | Nachtmerrie | 悪夢 | Pesadelo | Painajainen | Mardröm | 恶梦