'Biweekly' Versus 'Semiweekly'

Does anyone know what these words mean?

Mignon Fogarty
3-minute read
Episode #117

I have some friends who work in New York, and a couple of years ago they received a notice that said they were going to be paid biweekly from now on. The problem was that nobody could tell what “biweekly” meant, and their human resources department reported being inundated with calls from confused employees. 

How to Remember the Definitions of 'Bi-' and 'Semi-'

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“Semi-” means “half.” You can try to remember that by remembering that semisweet chocolate is only half sweet, and semiannual sales happen twice a year. 

“Bi-” can mean both “two” and “twice.” A bicycle has two tires, and the bicentennial happens after two hundred years, but a biannual event happens twice a year. 

A listener named Eric pointed out that these terms are relatively set in the mortgage industry. A bimonthly payment is paid two times a month, but a biweekly payment is not two times a week as you might presume if you were trying to adhere to just one meaning for the prefix “bi-.” No, a biweekly payment in the mortgage industry apparently happens every two weeks. The Merriam-Webster website explains that the “ambiguity has been in existence for nearly a century and a half.” How frustrating!

Knowing the Definitions Doesn't Necessarily Help

The definition of 'biweekly' is typically 'every two weeks.'

At first glance, then, knowing the meaning of the prefixes doesn't help. Does a biweekly paycheck come every two weeks or twice a month? (Or twice a week as a hopeful person may wonder.)

My friends guessed that it meant they got a paycheck every two weeks, and they were right. As in the mortgage industry, the definition of “biweekly” is typically every two weeks. If they were going to get a check twice a month, HR probably would have said the payments would be bimonthly. But it’s confusing. 

The earliest example I can find in the Oxford English Dictionary has “biweekly” meaning “twice a week,” as our very hopeful employee may think, and as Garner’s Modern English Usage notes, “biannual" and “semiannual” both correctly mean “occurring twice a year.” The Merriam-Webster Dictionary of English Usage notes that the words can take on an industry-specific meaning too. They say that in publishing, “bimonthly” usually means every two months, but in education, “bimonthly” usually means twice a month. (4)

Few People Know the Difference: Avoid 'Biweekly' and 'Semiweekly'

The most important thing to notice here is that many people are confused about the meaning of words such as “biweekly” and “bimonthly.” 

Most style guides recommend avoiding these words. Instead, just use the phrases “twice a week” or “every other week.” (1, 2, 3, 4) It's more clear. So that’s your Quick and Dirty Tip: It’s much more important to be clear than to use the proper word if the proper word is just going to confuse people.


  1. O'Connor, P.T. “The Scoop on “bi” and “semi.” The Grammarphobia Blog. September 15, 2006, http://www.grammarphobia.com/blog/2006/09/the-scoop-on-bi-and-semi.html (accessed 9/27/2013).
  2. Brians, P. Common Errors in English Usage. Wilsonville: William, James & Co., 2003, p. 27.
  3. Garner, B. Garner's Modern English Usage. Oxford: Oxford University Press, 2016, p. 114.
  4. Merriam-Webster's Dictionary of English Usage. Springfield: Merriam-Webster, 1994, p. 184-85.

01 (227) image, Victor1558 at Flickr. CC BY 2.0.

Mignon Fogarty is Grammar Girl and the founder of Quick and Dirty Tips. Check out her New York Times bestseller, “Grammar Girl’s Quick and Dirty Tips for Better Writing.

About the Author

Mignon Fogarty

Mignon Fogarty is the founder of Quick and Dirty Tips and the author of seven books on language, including the New York Times bestseller "Grammar Girl's Quick and Dirty Tips for Better Writing." She is an inductee in the Podcasting Hall of Fame, and the show is a five-time winner of Best Education Podcast in the Podcast Awards. She has appeared as a guest expert on the Oprah Winfrey Show and the Today Show. Her popular LinkedIn Learning courses help people write better to communicate better.

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