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[peer-ee-od-ik] /ˌpɪər iˈɒd ɪk/
recurring at intervals of time:
periodic revivals of an interest in handicrafts.
occurring or appearing at regular intervals:
periodic visits by doctors to the village.
repeated at irregular intervals; intermittent:
periodic outbreaks of the disease.
Physics. recurring at equal intervals of time.
Mathematics. (of a function) having a graph that repeats after a fixed interval (period) of the independent variable.
  1. characterized by a series of successive circuits or revolutions, as the motion of a planet or satellite.
  2. of or relating to a period, as of the revolution of a heavenly body.
pertaining to or characterized by rhetorical periods, or periodic sentences.
Origin of periodic1
1635-45; < Latin periodicus < Greek periodikós. See period, -ic
Related forms
periodically, adverb
quasi-periodically, adverb
Can be confused
periodic, periodical.


[pur-ahy-od-ik] /ˌpɜr aɪˈɒd ɪk/
adjective, Chemistry.
of or derived from a periodic acid.
First recorded in 1830-40; per- + iodic Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for periodic
Contemporary Examples
Historical Examples
  • The periodic or compensating errors of the planets is another instance.

    Essays, First Series Ralph Waldo Emerson
  • But what was his surprise to observe that these alterations were not of an annually periodic character.

    Great Astronomers R. S. Ball
  • The periodic time of the moon is the interval required for one circuit of its orbit.

    Great Astronomers R. S. Ball
  • His hopes for the best had been but periodic interruptions to a chronic fear of the worst.

    A Pair of Blue Eyes Thomas Hardy
  • Juno was to at once begin her first contribution to periodic literature.

British Dictionary definitions for periodic


happening or recurring at intervals; intermittent
of, relating to, or resembling a period
having or occurring in repeated periods or cycles
Derived Forms
periodically, adverb
periodicity (ˌpɪərɪəˈdɪsɪtɪ) noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for periodic

1640s, from French périodique (14c.), from Latin periodicus, from periodus (see period).

Periodic table in chemistry (1889) is from notion of the arrangement, in which similar properties recur at intervals in elements in the same area as you read down the rows of the table. This sense of the word is attested from 1872 (periodic law).

Online Etymology Dictionary, © 2010 Douglas Harper
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periodic in Medicine

periodic pe·ri·od·ic (pĭr'ē-ŏd'ĭk)

  1. Having or marked by repeated cycles.

  2. Recurring at regular intervals.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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