So, I happen to be in the process of creating this research paper about a historic figure; I had used Google to search for a synonym of occasionally, and one of the words I stumbled across was “periodically”. Now, don’t get me wrong – I have heard of this word many times in the past; however, I have never known it to be used in the place of a word such as the former mentioned. Up until this point, I’ve only ever really used it in the denotation of “a regular occurrence”.

For that reason, I decided to genuinely find its listed definition – and, as it turns out, this word is a complete paradox. It simultaneously means two entirely different things – they do nothing less than completely contradict each other.

periodically | ˌpirē'ädək(ə)lē |


  • from time to time; occasionally: I will periodically check on your progress | the students received help from a friend only periodically.

  • at regularly occurring intervals: the newsletter is sent out periodically to update members | the lamps were periodically switched on and off at 30 minute intervals.

Would someone be willing to explain how I should use this word? I’m incredibly confused – is it even “proper” to use “periodically” so that it means both occasionally and regularly? Or, would it generally be more accepted to just use the common definition (which I assume is the latter)?

I’d appreciate any and all comments and answers! Thanks, everybody!

  • There doesn't seem to be a specific question here...
    – Drew
    Commented Mar 26, 2017 at 2:05
  • You’re right; sorry – I’m going to edit it now. What I generally wanted to know was how I should use the word “periodically” – I’m really confused about whether or not it’s proper to have a word which simultaneously contradicts itself. Is a common definition more appropriate to use? Or, would it be acceptable to use both (either) meanings?
    – Kit
    Commented Mar 26, 2017 at 2:14
  • 3
    "Periodically" implies a reasonably regular period between events, whereas "occasionally" implies a more random spacing of the events. (Keep in mind that even though there's a period, it is not necessarily specified precisely. As with most English words dealing with quantities, intervals, or distances, "periodically" can be precisely defined to the nanosecond, or instead very "loose" and imprecise.)
    – Hot Licks
    Commented Mar 26, 2017 at 3:06
  • The examples listed after the bullet for "at regularly occurring intervals" are stinkers. In the first example, Periodic updates is understood to mean they will happen irregularly, when needed. It is specifically used in contrast to monthly, etc. In the second example, periodically adds nothing besides an overall sense of vagueness to an already ambiguous description. If finding good examples of periodicity-periodically is really that hard, then I think you can assume that the restrictive usage is just about dead.
    – Phil Sweet
    Commented Mar 26, 2017 at 3:15
  • Consider "comets appear periodically in the night sky". Nobody thinks this means each comet will return at its appointed time. It means that comets will continue to appear from time to time into the distant future.
    – Phil Sweet
    Commented Mar 26, 2017 at 3:19

1 Answer 1


Here's a dictionary definition that makes the contradiction between the two definitions especially clear (American Heritage):

  1. Having or marked by repeated cycles: periodic oscillations.
  2. Happening or appearing regularly or from time to time: periodic dental checkups; periodic rain showers.

This happens sometimes. Language is sometimes imprecise. If you want to prevent misunderstandings, then take context into account and add clarifying language if necessary.

Let me know if you need examples of how to do that.

  • What also happens sometimes is that adverb-adjective pairs drift apart in meaning, and this has certainly happened here. Periodic does imply regularity and pattern, as in the periodic table, which I look at periodically. Which is not to say I look at it period by period. en.wikipedia.org/wiki/Period_(periodic_table)
    – Phil Sweet
    Commented Mar 27, 2017 at 0:33
  • @PhilSweet - A sine wave is periodic. It couldn't be more regular. The first American Heritage meaning fits perfectly (periodic oscillations). Commented Mar 27, 2017 at 5:50
  • Maybe we could agree that, as @PhilSweet says, "Periodic does imply regularity and pattern", but that this regularity doesn't need to be (though it can be) mathematically precise. For example if I say "I regularly check in on my neighbour", this could mean "once or twice a week, at various times". In other words, periodic implies regularity, but regularity itself is an ambiguous concept. Commented Nov 22, 2017 at 10:46

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