What are classification of nightmare?

Nightmares are severe anxiety dreams where the fear and the issues in the dream are so intense that they usually wake up the dreamer. Some of these are warning dreams - predictions, death of someone you know or physical illness, (some impending disaster). Others are guilt dreams, when the dreamer is not the victim, but the murderer or the one who has hurt someone else (expressing guilt the dreamer is repressing). Anxiety dreams are similar to nightmares in themes and feelings of fear but not as intense. The dreamer can feel anxiety (and the fear can linger) even if he does not recall what evoked them. These dreams are disturbing but do not cause the dreamer to awaken in fright.