Period or periodic may refer to:

Language and literature

• Full stop, a punctuation mark indicating the end of a sentence or phrase
• Periodic sentence, a sentence that is not grammatically complete until its end
• The final book in Dennis Cooper's George Miles cycle of novels

Science and mathematics

• Menstruation, a phase of the menstrual cycle in which the uterine lining is shed
• Orbital period, a concept in astronomy.
• Period (gene), a gene in Drosophila involved in regulating circadian rhythm
• Period (geology), a subdivision of geologic time
• The period of a periodic function
• Period (number), a concept in mathematics
• Period (periodic table), a horizontal row of the periodic table
• Periodic acid, an oxoacid of iodine
• Period (physics), the reciprocal of frequency
• Period of orbit

Other meanings

• Period (music), a concept in musical composition
• Periodicity, the quality of occurring at regular intervals
• For historical period, see List of time periods

See also

• Periodization

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