Dream

The occurrence of ideas, emotions, visual imagery, and other sensations during sleep. Some dreams may be recalled on awakening; others may not be.

Any train of thoughts, images, or fancies that pass through the mind during sleep. There are many diverse beliefs about the nature of dreams, some dating from antiquity. Others go back to the 19th century and are associated with the rise of psychology as a separate subject within medicine. It was not until the 1950s that a laboratory technique was devised to study dreams.

Many ancient people believed that during sleep the soul left the body to live for a time in a special dream world. Because humans were thought to be without souls at this time, sleepers were never awakened lest their souls be lost on their hurried return home to the body. In classical Greece, dreams became associated with healing, and many sick people went to a special temple to sleep through the night to take the dream cure.