Movement of a pendulum or oscillating body between two extreme positions (A' and A'').
The balance of a mechanical watch generally makes five, six or eight vibrations per second, respectively 18,000, 21,600 and 28,800 vibrations/hour (2.5 Hz/3 Hz/4 Hz). The most advanced make 10 vibrations per second or 36,000 vibrations/hour (5 Hz). The precision of a mechanical watch is a direct consequence of the higher number of vibrations. In comparison, the quartz in an electronic watch usually vibrates at a frequency of 32,768 Hz (generally abbreviated to 32 kHz).
An oscillation ("tick-tock") equals two vibrations (although oscillation is sometimes incorrectly used to refer to a vibration).