Period may refer to:

Common uses
Period (punctuation)
Era, a length or span of time
Menstruation, commonly referred to as a "period"

Arts, entertainment, and media
Period (music), a concept in musical composition
Periodic sentence (or rhetorical period), a concept in grammar and literary style.
Period, a descriptor for a historical or period drama
Period, a timeframe in which a particular style of antique furniture or some other work of art was produced, such as the "Edwardian period"
Period (Another American Lie), a 1987 album by B.A.L.L.
Period (mixtape), a 2018 mixtape by City Girls
Period, the final book in Dennis Cooper's George Miles cycle of novels
Periods., a comedy film series

Mathematics
In a repeating decimal, the length of the repetend
Period of a function, length or duration after which a function repeats itself
Period (algebraic geometry), numbers that can be expressed as integrals of algebraic differential forms over algebraically defined domains, forming a ring

Science
Period (gene), a gene in Drosophila involved in regulating circadian rhythm
Period (periodic table), a horizontal row of the periodic table
"Period-" or "per-iod-", in some chemical compounds, "per" refers to oxidation state, and "iod" refers to the compound containing iodine
Unit of time or timeframe
Period (geology), a subdivision of geologic time
Period (physics), the duration of time of one cycle in a repeating event
Orbital period, the time needed for one object to complete an orbit around another
Rotation period, the time needed for one object to complete a revolution
Wavelength, the spatial period of a periodic wave
Sentence (linguistics), especially when discussing complex sentences in Latin syntax

Other uses
Period (school), a class meeting time in schools
Period (ice hockey), a division of play in an ice hockey game
Accounting period, often shortened to "period" in business, an accounting timeframe analogous to a month

See also
Duration (disambiguation)
Full stop (disambiguation)
Periodicity (disambiguation)
Periodization
List of time periods
History by period