A tic is a term defining sudden, rapid, repetitive, and involuntary muscle contractions (motor tics) or sounds (vocal tics). These movements or sounds are typically very brief, rarely lasting longer than one second. Examples of tics include blinking, facial twitches, sniffing, or throat clearing. Tics usually occur in episodes, with intervening periods (remissions) when tics are not observed. Tics can be suppressed for short periods; however, their severity may increase with emotional changes and stress.