Abbreviation at End of Sentence: Use of Periods and Other Punctuation
If an abbreviation ending in a period appears at the end of a sentence, don’t add another period to end the sentence. Use just one period, not two.
- Incorrect: They serve cakes, cookies, etc..
Correct: They serve cakes, cookies, etc. - Incorrect: The bell rang at 3 a.m..
Correct: The bell rang at 3 a.m. - Incorrect: We haven’t yet reviewed the paper by Dash et al..
Correct: We haven’t yet reviewed the paper by Dash et al. - Incorrect: Poco works at Nusquam Inc..
Correct: Poco works at Nusquam Inc.
Of course not all abbreviations end in periods. If an abbreviation does not itself end in a period, place a period after it as usual to end the sentence.
- Correct: Rita wants a car with a high rpm.
- Correct: Minerva Dash is our new CEO.
- Correct: The caterpillar measured 20 cm.
Abbreviation in parentheses or brackets
If an abbreviation ending in a period appears within parentheses or brackets at the end of a sentence, place another period after the closing parenthesis or bracket to mark the end of the sentence.
- Incorrect: They serve all kinds of confectionary (cakes, cookies, etc.)
Correct: They serve all kinds of confectionary (cakes, cookies, etc.). - Incorrect: Applications will not be accepted after the deadline (6 p.m.)
Correct: Applications will not be accepted after the deadline (6 p.m.). - Incorrect: To cite an edited book, use the abbreviation ed. or eds. in parentheses: M. Dash (ed.)
Correct: To cite an edited book, use the abbreviation ed. or eds. in parentheses: M. Dash (ed.).
But if the sentence with the abbreviation is entirely enclosed in parentheses, don’t add another period to end the sentence. (The sentence has already ended within the parentheses.)
- Incorrect: If you’re ever in Nusquam, you should visit the Pouthena Bakery on Nulle Street. (They serve the best cakes, cookies, etc.).
Correct: If you’re ever in Nusquam, you should visit the Pouthena Bakery on Nulle Street. (They serve the best cakes, cookies, etc.) - Incorrect: Night comes early in winter. (It gets dark by 4 p.m.).
Correct: Night comes early in winter. (It gets dark by 4 p.m.) - Incorrect: It has been conclusively established that life is meaningless. (For a detailed discussion, see Dash et al.).
Correct: It has been conclusively established that life is meaningless. (For a detailed discussion, see Dash et al.)
Ellipsis after abbreviation
If an abbreviation ending in a period is followed by an ellipsis, don’t omit the period for the abbreviation. You need four periods, not three: one for the abbreviation and three for the ellipsis.
- Incorrect: Marine mammals are seals, whales, otters, etc. . .
Correct: Marine mammals are seals, whales, otters, etc. . . . - Incorrect: Pesticides harm butterflies, bees, etc. . . They also contaminate groundwater.
Correct: Pesticides harm butterflies, bees, etc. . . . They also contaminate groundwater.
If a sentence ends in an abbreviation followed by an ellipsis, use just one period for both the abbreviation and the end of the sentence, and three for the ellipsis: four periods in all, not five.
- Original: Wake up at 6 a.m., when the day is still full of possibility. Having completed all your work by afternoon, have a calm and relaxing evening. You can then go to bed early. Or so they say. We all know the day is over at noon.
Shortened: Wake up at 6 a.m. . . . You can then go to bed early. . . . We all know the day is over at noon.
Abbreviation in quotation marks
If an abbreviation ending in a period appears within quotation marks at the end of a sentence, don’t add another period. The period after the abbreviation suffices to mark the end of the sentence.
- Incorrect: Anita replied, “We close at 9 a.m.”.
Correct: Anita replied, “We close at 9 a.m.” - Incorrect: Poco said, “I’ll send you a list of requirements, costs, etc.”.
Correct: Poco said, “I’ll send you a list of requirements, costs, etc.”
Even if the abbreviation appears in quotes within quotes (i.e., within single and then double quotation marks), one period suffices. Don’t add another period to end the sentence.
- Lulu said, “Rita clearly told me ‘9 a.m.’”
Question mark and exclamation point after abbreviation
Use question marks and exclamation points as usual after an abbreviation that ends in a period. (Don’t omit the period.)
- Correct: Did you say she called at 4 a.m.?
- Correct: Where can I buy balloons, flags, masks, etc.?
- Correct: Does Farley still work at Nusquam Inc.?
- Correct: Is midnight 12 a.m. or 12 p.m.?
- Correct: I can’t believe it’s 4 a.m.!
Other punctuation with abbreviations
Use commas, dashes, semicolons, and other punctuation marks as usual after an abbreviation that ends in a period.
- At 4 a.m., the bell rang.
- We sell party supplies—balloons, flags, masks, etc.—at discounted rates.
- She said it was 4 a.m.; I believed her.
- Business hours are 9 a.m.–6 p.m.