The two terms chronograph and chronometer are quite often confused, although they have altogether different meanings. A chronograph is a type of complication. A chronograph complication, is the ability of the watch movement to function as a stopwatch. A chronometer is a watch or clock in which the movement has been tested and certified to operate within a certain standard of accuracy by the COSC (Contrôle Officiel Suisse des Chronomètres). The concepts are different but not necessarily mutually exclusive; a watch may be a chronograph watch, a chronometer, both, or neither.