In a world in which we are inundated with information sometimes the most simple of things become complicated. One of the most common mistakes we hear is the confusion between two very different watches whose only real similarity is found in the first 5 letters of their name.
A chronograph is a watch that indicates the hours, minutes and seconds of time, but includes an additional system that allows a chronograph seconds hand to be started, stopped and returned to zero on request, in order to measure a specific period of time. Usually with additional sub counters to measure the minutes and hours.
Breguet Classique Chronographe 5287.
A chronometer is a timepiece for measuring time to within a specific level of accuracy tested over a set period of time in different positions and different temperatures and awarded a certificate by a neutral organisation qualifying for the criteria laid down in standard; ISO 3159, or an equivalent. (See COSC)
Ferdinand Berthoud FB1 Chronomètre