A thought was an idea or concept created by the mental activity of the mind. The process of creating a thought was called thinking.
The Talosians of Talos IV could read the thoughts of their specimens. After reading Vina's thoughts, as well as her feelings and her dreams of what would be a perfect man, the Talosians picked CaptainChristopher Pike. Furthermore, the Talosians could create an illusion out of an individual's thought for them to experience, such as the crew of the USS Enterprise thinking they had found the survivors from the crashedSS Columbia. (TOS: "The Cage")
According to Spock in 2267, Jackson Roykirk's dream was to build a perfect thinking machine, capable of independent logic. The result was the prototypeNomad, the best thinking machine that could be engineered which was launched in the early 2000s. (TOS: "The Changeling")
The Traveler claimed thought was the basis of all reality. (TNG: "Where No One Has Gone Before")
Sentientspecies, such as Humans, have the ability to distinguish between thought and reality. (TNG: "Where No One Has Gone Before")
Q once said to CaptainJean-Luc Picard that he "thought by now you would have scampered back to your own little star system." (TNG: "Hide And Q")
TelepathicLwaxana Troi was forced to terminate the employment of her valet, Mr.Xelo, because he was strongly attracted to her and his thoughts became truly pornographic. (TNG: "Haven")
In 2364, despite the holographicMinuet being a computer-generated image, the things she thought were among her aspects which seemed so real to William T. Riker. (TNG: "11001001")
In most Betazoids, their telepathic gifts developed at adolescence, however, occasionally a child was born with their telepathic abilities switched on. Most Betazoids born that way never led a normal life as the noise of other peoples' thoughts and feelings were overwhelming, incomprehensible, and painful, especially to a child. (TNG: "Tin Man")
In the 2330s, at Omicron Theta colony, DoctorNoonien Soong scanned the synaptic patterns of the colonists' temporal lobes and programmed them into Data's neural nets. As a result, Data could have been said to have possessed, to a degree, their thoughts. (TNG: "Silicon Avatar")
