A tic is a repeated, impulsive action, almost reflexive in nature, which the actor feels powerless to control or avoid. Tics can be triggered by an emotional state (stress is a common trigger) or sensation, or can happen for no obvious reason.

General types of tics include verbal tics, facial tics, and other muscular tics. Physical and psychological therapy and meditation can cause tics to go away, often permanently.

Muscular tics look something like twitches or quick grimaces, and often affect the eyes and hands. Muscular tics can affect multiple muscles at once. Some forms of stuttering are muscular tics which cause a tightening of the throat, tongue, or vocal cords when speaking or preparing to speak.

Verbal tics can include certain phrases which are uttered uncontrollably, or ejaculations such as curses or grunts in the middle of sentences. Specific verbal tics may include compulsive swearing (Coprolalia), the symptom most often associated with Tourette syndrome, though most people with the disorder never experience this - it actually is quite rare and only occurs in about ten to fifteen percent of cases.

There is some confusion in film and literature about tics. In comedies, a person with muscle tics may haplessly raise their hand at an obviously inappropriate time and suffer the consequences. This is far-fetched. Tics are conscious actions taken by the sufferer to alleviate the onset of some kind of discomfort. The arm is not just thrust up into the air as if the sufferer were possessed.

Muscle tics are physical actions that alleviate some kind of nerve discomfort in an area of the body. A sufferer may have discomfort in their bicep that can only be satisfied when the muscle is flexed. Massaging the muscle, applying hot or cold, and other external treatments are ineffective.