A lucid dream is any dream during which the dreamer is aware that they are dreaming.
During lucid dreaming, the dreamer may be able to exert some degree of control over the dream characters, narrative, and environment.
The term 'lucid dream' was coined by Dutch author and psychiatrist Frederik van Eeden in his 1913 article A Study of Dreams, though descriptions of dreamers being aware that they are dreaming predates the term.
In Eastern thought, cultivating the dreamer's ability to be aware that he or she is dreaming is central to both the Tibetan Buddhist practice of dream Yoga, and the ancient Indian Hindu practice of Yoga nidra. The cultivation of such awareness was common practice among early Buddhists.