Full Stops (Periods) in Abbreviations (Grammar Lesson)

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The Quick Answer
Abbreviations can be written with or without periods () full stops (). Often, you have a choice. In other words, you can write:
  • C.N.N. or CNN
  • e.g. or eg
Whatever format you use, be consistent. The most common format is to omit periods in uppercase abbreviations (for example, CNN, ITN) but to use them in lowercase abbreviations (for example, e.g., p.m.).

If the abbreviation is a proper noun (e.g., a company name), copy the official version.

This guidance does not apply to titles such as Mrs., Mr., Ms., Dr., Prof., Capt., Gen., Sen., Rev., Hon., and St.

Read more about using periods in titles.

Periods (Full Stops) in Abbreviations

It is considered untidy to mix abbreviations with periods and ones without periods in the same article. These two examples have been marked as correct because the writer has been consistent.
  • The band toured around the UK and the USA last year.
  • The band toured around the U.K. and the U.S.A. last year.
These next two examples are marked wrong because the writer has been inconsistent.
  • It was only shown on ITV and not B.B.C.
  • (This is an inconsistent use of full stops (periods). It is considered untidy.)
  • The M.D. asked her PA to clean her car.
  • (Untidy)

The Tendency: Use Periods Only in Uppercase Abbreviations

Abbreviations made up of capital letters tend not to have periods, but abbreviations made up of lowercase letters tend to have them. For example:
  • BBC
  • (British Broadcasting Corporation)
  • LRS
  • (Linear Recursive Sequence)
  • CBS
  • (Columbia Broadcasting System)
  • a.m.
  • (ante meridiem - before midday)
  • p.m.
  • (post meridiem - after midday)
  • i.e.
  • (id est - that is)
  • e.g.
  • (exempli gratia - for the sake of an example)
  • p.p.
  • (per procurationem - by the agency of)
Note: This is a tendency not a rule.

If the abbreviation is a proper noun (e.g., a company name), copy the official version. For example:
  • Our team was hosted by the Italian club A.S. Livorno Calcio.
  • ("A.S. Livorno Calcio" (with periods) is the name shown on the logo and in all correspondence.)
  • The shop will be taken over by the clothing company s.Oliver in June.
  • ("s.Oliver" is the official version.)
  • We will meet at P.F. Chang's in Tokyo.
  • ("P.F. Chang" is the official version.)
Note: Do not worry about this point. There are very few companies who use periods in their names. I mean almost none.

Do Not Use Two Periods If Your Sentence Ends with an Abbreviation

If your sentence ends with an abbreviation (including a contraction like "etc.") that ends with a period, do not use a second period to show the end of the sentence. However, other end marks (such as question marks, exclamation marks) should be used. For example:
  • I need milk, bread, cheese, etc.
  • She moved from I.T.V. after an irresistible offer from the B.B.C.
  • She moved from I.T.V. after an irresistible offer from the B.B.C..
  • (Logically, this is correct, but it is too unwieldy.)
  • Will she move back to the B.B.C.?
  • (This is correct, but it looks a little scruffy. To avoid this, use BBC instead of B.B.C.)
The only exception to doubling up end marks with periods is ellipsis (...). For example:
  • Standing tall and with the Lord's Prayer mumbling across our lips, we entered the chamber...."
  • (This ends in four dots: three for the ellipsis and one to end the sentence.)
Ready for the Test?
Here is a confirmatory test for this lesson.

This test can also be:
  • Edited (i.e., you can delete questions and play with the order of the questions).
  • Printed to create a handout.
  • Sent electronically to friends or students.

See Also

Ms., Miss., or Mrs.? Using AD, BC, BCE and CE Periods (full stops) in titles and contractions Forming the plurals of abbreviations