# Period

From AMS Glossary

## period

Any function of time

*f*(*t*) is periodic with period*t*if*f*(*t*) =*f*(*t*+ τ) for all times*t*, where τ is the smallest number for which this equality holds.Without qualification, period often means temporal period, but could mean spatial period (wavelength), the repeat distance of a spatially periodic function.

*See*frequency.