This is the property of a pendulum or balance wherein it is possible for a certain amount of time that the pendulum or balance is not affected by the amplitude of the oscillator. To put simply, a pendulum or balance has the property of isochronism wherein it takes equal time to complete a swing regardless of the intensity or the level of the swing. The importance of an isochronal oscillator is immeasurable in timekeeping because without one you cannot make a timepiece. An isochronal oscillator can be a balance, balance spring, pendulum, or a quartz crystal.
Derived from the greek words iso and chronos, Isochronism means “in the same time”.