A sequence of events is isochronous if the events occur regularly, or at equal time intervals. Isochronous timing differs from synchronous timing, in that the latter refers to relative timing between two or more sequences of events. The term isochronous is used in different technical contexts, but often refers to the primary subject maintaining a certain interval, despite variations in other measurable factors in the same system.
- In dynamical system theory an oscillator is called isochronous if the frequency is independent of its amplitude. For example, as noted by Galileo in the late 16th century, the oscillation period of a pendulum is constant, regardless of the angle of the swing. This is used in timekeeping.
- In horology, a mechanical clock or watch is isochronous if it runs at the same rate regardless of changes in its drive force, so it keeps correct time as the mainspring unwinds. This includes clocks that use a pendulum.
- In telecommunications, an isochronous signal is one where the time interval separating any two corresponding transitions is equal to the unit interval or to a multiple of the unit interval; but phase is arbitrary (and in some systems may change slowly over time).
- The term is also used in data transmission to describe cases in which corresponding significant instants of two or more sequential signals have a constant phase relationship.
- Isochronous burst transmission is used when the information-bearer channel rate is higher than the input data signaling rate
- In power generation, isochronous means that the frequency of the electricity generated is 'flat' or constant, and there is zero generator droop. (See Synchronization (alternating current))
- In the Universal Serial Bus used in computers, isochronous is one of the four data flow types for USB devices
- In particle accelerators an isochronous cyclotron is a cyclotron where the field strength increases with radius to compensate for relativistic increase in mass with speed
- An isochrone is a contour line of equal time, for instance, in geological layers, tree rings or wave fronts. An isochrone map or diagram shows such contours.
- In linguistics, isochrony is the postulated rhythmic division of time into equal portions by a language.
- In neurology, isochronic tones are regular beats of a single tone used for brainwave entrainment.