End Punctuation: Periods

Periods are used at the ends of sentences, after certain abbreviations, and sometimes in vertical lists. Click on one of the uses to read a description of that use and some examples to illustrate it.

• Periods used to end a sentence.
• Periods used with quotation marks.
• Periods used with parentheses and brackets.
• Periods used after abbreviations.
• Periods used in vertical lists.

Use a period to end a sentence.

Periods are used to mark the end of declarative and imperative sentences. Here are two examples of periods at the end of sentences:

I revised my essay (Declarative Sentence)

Drive slowly (Imperative Sentence)

Periods go inside quotation marks.

When all or part of a sentence is a quotation, the period at the end of the sentence goes inside the quotation marks.

"It's unfortunate," David continued, "that no one understands the importance of geometry anymore"

"I remember that Jim was nearly exhausted," Marlene recounted, "from staying up all night to finish 'Cathedral'"

A promise is an example of what J. L. Austin calls an "explicit performative"

Periods used with parentheses or brackets.

If parentheses are used to enclose a complete sentence that is not part of another sentence, as in the following example, then the period goes inside the parentheses:

Flora insisted rather angrily upon taking the long route. (I didn't think it wise to oppose her) So it took us nearly an hour to reach the cabin.

If the parenthetical element is part of a sentence, as in these examples, then the period goes outside the parentheses or brackets:

At the end of the story, Jason admits his guilt: "It was I who stole the diamond from her [Julie]"

In a 1973 addendum to his original essay, Bakhtin provides a long catalogue of such recurring patterns (the chronotype of the road, of the trial, of the provincial town, and so on)" (Holquist, Michael. Dialogism: Bakhtin and His World. London: Routledge, 1990. 112.)

Use a period after certain abbreviations

Use periods after the following common abbreviations:

• Ms., Mr., Mrs.
• M.D., Ph.D., Dr., B.S., B.A.
• A.M., a.m., P.M., p.m., B.C., A.D.

The capitol of the United States is Washington, D.C.

Notice that there are no spaces between the letters and the periods of abbreviations. Also, remember that abbreviations are different from acronyms.

When to use periods in vertical lists.

If you use numeral or letters to enumerate items in a vertical list, use a period after the numeral or letter:

• 1 cultures
• 2 nationalities
• a symbols
• b metaphors

In general, periods are not necessary following items in a vertical list unless one or more of the items of the list are complete sentences.