In horology terms, a complication in a mechanical timepiece is a any feature beyond that of a simple hours, minutes, and seconds movement. Examples of complications include:

• 24 hour watch
• Automatic watch
• Chronograph
• Date display
• Day of week display
• Double chronograph
• Equation of time
• Hack feature
• Minute repeater
• Month display
• Moon phases
• Perpetual calendar
• Power reserve
• Quickset date
• Tourbillon