When You Need Periods After Abbreviations

Putting periods after abbreviations (or not) is a little-known difference between British English and American English. Here's when you need periods and when you don't.

Mignon Fogarty

A reader named Dennis K. asked whether you always put periods after abbreviations or whether it’s different depending on which letters from the word are used in the abbreviation. Someone told him that abbreviations should only use a period if it doesn’t end with the last letter of the original word, but he’d never heard that before, so he was wondering if it is right.

Putting periods after abbreviations (or not) is a little-known difference between British English and American English.

In American English, we always put a period after an abbreviation; it doesn’t matter whether the abbreviation is the first two letters of the word (as in Dr. for Drive) or the first and last letter (as in Dr. for Doctor).

British writers, however, make a distinction: abbreviations that are written with the first and last letter of the word (as in Dr. for Doctor and Mr. for Mister) do not get a period.

Here are examples of how the abbreviations differ:

Periods After Abbreviations British American


“Personal Names with ‘Saint’ or ‘St.’” The Chicago Manual of Style, 16th edition. 10.27 http://www.chicagomanualofstyle.org/16/ch10/ch10_sec027.html (subscription required, accessed September 17, 2014)

“Punctuation in Abbreviations.” Oxford Dictionaries. http://www.oxforddictionaries.com/us/words/punctuation-in-abbreviations-american (accessed September 17, 2014)


About the Author

Mignon Fogarty

Mignon Fogarty is the founder of the Quick and Dirty Tips network and creator of Grammar Girl, which has been named one of Writer's Digest's 101 best websites for writers multiple times. The Grammar Girl podcast has also won Best Education Podcast multiple times in the Podcast Awards, and Mignon is an inductee in the Podcasting Hall of Fame. Mignon is the author of the New York Times best-seller "Grammar Girl's Quick and Dirty Tips for Better Writing" and six other books on writing. She has appeared as a guest on the "Oprah Winfrey Show" and the "Today Show" and has been featured in the New York Times, Business Week, the Washington Post, USA Today, CNN.com, and more. She was previously the chair of media entrepreneurship in the Reynolds School of Journalism in Reno, NV. She hates the phrase "grammar nazi" and loves the word "kerfuffle." She has a B.A. in English from the University of Washington in Seattle and an M.S. in biology from Stanford University. Mignon believes that learning is fun, and the vast rules of grammar are wonderful fodder for lifelong study. 

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