chrono-, chron-

(Greek: time, times; sequence of times)

synchronograph
An automatic recording telegraph worked by an alternating electric current, with a synchronously moving strip of perforated paper.
synchronology
Combined or comparative chronology; arrangement of events according to dates, those of the same date being placed or treated together; a comparative chronology.
synchronous
1. Existing or happening at the same time, simultaneously; coincident in time; belonging to the same period, or occurring at the same moment, of time; contemporary; simultaneous.
2. Relating to or treating of different events or things belonging to the same time or period; involving or indicating contemporaneous or simultaneous occurrence.
3. Recurring at the same successive instants of time; keeping time with; going on at the same rate and exactly together; having coincident periods, as two sets of vibrations or the like.
4. Of a satellite: rotating round the parent planet at the same rate as the planet rotates.
5. Of an orbit: such that a satellite in it is synchronous.
synchrony
The simultaneous appearance of two separate events.
synchrotron
In nucleonics, a machine that accelerates charged particles in circular orbits by varying the frequency of the accelerating voltage and also magnetic field so as to maintain a circular orbit.
tautochrone
That curve upon which a particle moving under the action of gravity (or any given force) will reach the lowest (or some fixed) point in the same time, from whatever point it starts.

A tautochrone or isochrone curve is the curve for which the time taken by a frictionless particle sliding down it under uniform gravity to its lowest point is independent of its starting point. The curve is a cycloid, and the time is equal to π times the square root of the radius over the acceleration of gravity.

tautochronism
Occupying the same time; pertaining to, or having the properties of, a tautochrone.
tautochronous
Having the character of a tautochrone; occupying the same time, isochronous.
tephrochronological
tephrochronology
The dating of volcanic eruptions and other events by studying layers of tephra.