(mathematics) Any function whose value repeats after the regular addition of a period to its independent variable; i.e., a function ƒ such that, for some positive constant p, ƒ(x + p) = ƒ(x) for all x.

(idiomatic) A length of time during which rules or penalties are waived or deferred.

a school period in which a student has free time, i.e., is not enrolled in a class.

(astronomy) Taking over 200 years to complete an orbit; especially said of comets.

Any of certain species of cicadas, especially in genus Magicicada, which are known for their 17- and 13-year life-cycles, during most of which they develop underground, emerging in large numbers for a short time as large and audible adults, all those emerging in a year constituting a brood.

(physics) Half of the period of a wave etc; typically the time taken for part of a wave to be replaced by a similar part that is out of phase.

plural of periodic table

(of an astronomic object) The time taken to rotate about its axis relative to the background stars.

rotational period

Time period between the receipt of the letter of dismissal and the last working day.