a portion of time of indefinable length: he spent a period away from home a portion of time specified in some way: the Arthurian period, Picasso's blue period (as modifier): period costume a nontechnical name for an occurrence of menstruation a unit of geological time during which a system of rocks is formed: the Jurassic period a division of time, esp of the academic day the time taken to complete one cycle of a regularly recurring phenomenon; the reciprocal of frequency
Symbol: Tthe time interval between two successive maxima or minima of light variation of a variable star one of the horizontal rows of elements in the periodic table. Each period starts with an alkali metal and ends with a rare gas
Comparegroup 11 a completion or end
WordReference Random House Learner's Dictionary of American English © 2026
pe•ri•od /ˈpɪriəd/USA pronunciation
n. [countable]
adj. [before a noun]
interj.
WordReference Random House Unabridged Dictionary of American English © 2026- an extent of time meaningful in the life of a person, in history, etc.:a period of illness.
- a round of time marked by some repeating event or action:the rainy period.
- Sportany of the parts into which something, as a school day, etc., is divided:She has gym in the first period.
- Grammarthe point or character (.) used to mark the end of a declarative sentence or to indicate an abbreviation;
a full stop. - Physiology
- an occurrence of menstruation.
adj. [before a noun]
- noting or relating to a certain historical period:a period play.
interj.
- (used to express the opinion that a decision is final):I forbid you to go, period.
pe•ri•od
(pēr′ē əd),USA pronunciation n.
adj.
interj.
- a rather large interval of time that is meaningful in the life of a person, in history, etc., because of its particular characteristics:a period of illness;a period of great profitability for a company;a period of social unrest in Germany.
- any specified division or portion of time:poetry of the period from 1603 to 1660.
- a round of time or series of years by which time is measured.
- a round of time marked by the recurrence of some phenomenon or occupied by some recurring process or action.
- the point of completion of a round of time or of the time during which something lasts or happens.
- Educationa specific length of time during school hours that a student spends in a classroom, laboratory, etc., or has free.
- Sportany of the parts of equal length into which a game is divided.
- the time during which something runs its course.
- the present time.
- Grammarthe point or character (.) used to mark the end of a declarative sentence, indicate an abbreviation, etc.;
full stop. - Grammara full pause, as is made at the end of a complete sentence;
full stop. - Poetry, Rhetorica sentence, esp. a well-balanced, impressive sentence:the stately periods of Churchill.
- Poetry, Rhetoric, Grammara periodic sentence.
- Physiologyan occurrence of menstruation.
- Physiologya time of the month during which menstruation occurs.
- Geologythe basic unit of geologic time, during which a standard rock system is formed: comprising two or more epochs and included with other periods in an era. See table under geologic time.
- Physicsthe duration of one complete cycle of a wave or oscillation;
the reciprocal of the frequency. - Music and Dancea division of a composition, usually a passage of eight or sixteen measures, complete or satisfactory in itself, commonly consisting of two or more contrasted or complementary phrases ending with a conclusive cadence.
- Astronomy
- AstronomyAlso called period of rotation. the time in which a body rotates once on its axis.
- AstronomyAlso called period of revolution. the time in which a planet or satellite revolves once about its primary.
- MathematicsSee under periodic (def. 5).
- Poetry[Class. Pros.]a group of two or more cola.
adj.
- noting, pertaining to, evocative of, imitating, or representing a historical period or the styles current during a specific period of history:period costumes; a period play.
interj.
- (used by a speaker or writer to indicate that a decision is irrevocable or that a point is no longer discussable):I forbid you to go, period.
- Greek períodos circuit, period of time, period in rhetoric, literally, way around. See peri-, -ode2
- Medieval Latin periodus, Latin
- Middle French)
- late Middle English periode (1375–1425
- 1.See corresponding entry in Unabridged See age.
- 2.See corresponding entry in Unabridged term.
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