A nightmare is a disturbing dream that often causes feelings of fear, anxiety, or distress. These dreams can involve frightening scenarios, such as being chased or falling, and may lead to waking up suddenly. Nightmares are common in both children and adults, and they can be triggered by stress, trauma, or certain medications. In the realm of horror, nightmares can also refer to themes explored in literature and film. They often serve as a way to confront fears and explore the darker aspects of the human psyche. Works featuring nightmares can evoke strong emotional responses and provoke thought about the nature of fear itself.