Dream
A dream was a series of sensory inputs and emotions involuntarily occurring in the mind during REM sleep. Generally, only those sensory inputs that were pleasant or neutral to the dreamer were referred to as dreams; those that were disturbing or frightening were specifically known as "nightmares". Dream analysis held that people who appeared in a dream represented facets of the dreamer's self. () According to Federation counselors, dreams could contain valuable insights. Ezri Dax once explained, "Things that don't seem to make sense are actually the key to what your unconscious is trying to tell you." (; )

AIs sometimes had the ability to dream added to their programming. Noonian Soong added the ability to dream to Data. ()

Someone dreaming often saw people they knew acting very differently from their normal ways. In November 2151, aboard a damaged , with little hope of rescue (believing  to have been destroyed), Malcolm Reed dreamt that, while recovering in Enterprises sickbay, he received amorous attention from T'Pol, impressed with his "heroic" actions, but was awakened just as the Vulcan was about to kiss him. Not long after, having actually been rescued, he asked T'Pol if she was supposed to "say something" about "heroics" - upon hearing her less-than-amused response, he smiled, as it signaled that he was not dreaming and had in fact survived. ()

Not longer after, that same year, a group of Vulcans part of an offshoot group known as the V'tosh ka'tur paid a visit to the Enterprise. These Vulcans refused to submit to the traditional Vulcan practice of repressing all emotions. One of them, Tolaris, suggested that T'Pol forego her nightly meditation as an experiment and that she would find her dreams to be far more interesting if she did. T'Pol followed his advice, but ultimately found the dreams she had to be unsettling in nature instead. Later, after Tolaris had left the vessel, she asked Captain Jonathan Archer if he ever dreamt. He agreed that he did and that sometimes they were even in color. She then asked if it was enjoyable for him. He agreed that most nights it was and she replied that she envied him. ()

In 2257, Jett Reno told Paul Stamets after awaking from unconsciousness that she had been dreaming about playing drums for Prince. ()

In 2268, amnesiac Captain James T. Kirk was plagued by dreams. After joining with his wife, the tribal priestess Miramanee of the planet Amerind, he was happy but the dreams had kept his mind from being completely at peace. ()

In 2367, the crew of the  went slowly insane as they were unable to dream while trapped in a Tyken's Rift. ()

In an alternate timeline, when Benjamin Sisko was knocked into a state of temporal displacement, his initial reappearance on Deep Space 9 was dismissed as a dream. ()

Worf once commented that Klingons dream about "things that would send cold chills down your spine and wake you in the middle of the night." ()

In 2373, Captain Jean-Luc Picard experienced a terrifying dream about his experiences with the Borg. The dream was apparently induced by the Borg's proximity. ()

In 2374, the  encountered the Dream Aliens, a species of aliens that lived out their lives in dreams. They became trapped in the same shared dreaming state the aliens lived in, experiencing "false awakenings" - a phenomenon where one dreams they have awakened from a dream, only to have transitioned into another dream - while trying to wake themselves up and escape. ()

Also in 2374, Seven of Nine was left to tend to Voyager while the rest of the crew was in stasis. Twenty-nine days into this, she reported in her personal log that her dreams had become disturbing. ()

In 2375, Nog asked Vic Fontaine if he dreamed when his program was off. In response, Vic only smiled ambiguously. ()

In 2376, The Doctor added a daydreaming subroutine to his program. ()

In 2399, retired Admiral Jean-Luc Picard had a dream featuring Data at Ten Forward of the Enterprise-D. ()

The android Soji Asha claimed to dream, something which Narek theorized might be a way to deal with the cognitive dissonance of believing she was Human while constantly bumping into evidence she was not. ()

Types of dreams
 Dismemberment dream (aka "dismantlement dream")
 Lucid dream
 Nightmare
 Vision

See also 
 The Clown
 The Interpretation of Dreams
 Unimatrix Zero
 Vision quest

External link 
 

de:Traum
Psychology
Sleep