1. The time T for one cycle. The time for a wavecrest to transverse a distance equal to one wavelength, or the time for two successive wavecrests to pass a fixed point. For a monochromatic wavetrain,
where f=frequency, =wavelength, and V=phase velocity. See Figure W-2.
2. A major standard geochronologic time unit; see stratigraphic classification and Appendix I.