Chronograph
Not to be confused with a chronometer.
A Chronograph is a watch with a built-in stopwatch.
For mechanical watches, this complication greatly adds to the complexity of the mechanisms involved. Each one built is a feat of engineering, a proud display of craftsmanship.
For digital watches, it's a nice bonus feature. The added complexity is in the IC, too small to see with the naked eye, barely any harder to mass produce than a plain watch's circuit, and taken for granted by the user. The engineering, while still impressive, is all in the initial design.
Some chronographs have a tachymeter.
Watches: Casio watches | Chronograph | NATO strap
