Unconscious means not awake or aware of what's happening around you. When someone gets knocked unconscious in a fall, their eyes close and they can't respond to voices or movement, almost like being in a very deep sleep they can't wake up from. Doctors can make patients unconscious during surgery using anesthesia so they won't feel pain or remember the operation.

The word also describes things you do without thinking about them. Your breathing is unconscious: you don't have to remind yourself to take each breath. When a practiced pianist plays a familiar song, her fingers move unconsciously across the keys while she thinks about the emotion of the music. These unconscious actions happen automatically, without deliberate thought.

In psychology, the unconscious (sometimes called the unconscious mind) refers to thoughts, feelings, and memories that influence your behavior even though you're not actively aware of them. You might feel nervous before a presentation without consciously knowing why, or instantly dislike a smell because it unconsciously reminds you of being sick once. Sigmund Freud made the unconscious mind famous by arguing that these hidden thoughts shape more of our behavior than we realize, though psychologists continue to debate exactly how this works.