The period, called a full stop in British English, ends every complete sentence that makes a statement. It also marks many abbreviations, and when a sentence ends with an abbreviation, that one period does both jobs.
English has many punctuation marks, but this one appears in almost every text you write. This short article covers its rules.
Rules for the period
The British name says what the period does: it brings a complete sentence to a full stop. It does not matter whether the sentence is short or long, simple or complex, or how many clauses it contains. As soon as the period comes, the sentence is finished. This applies to every complete sentence that makes a statement, rather than asking a question or making an exclamation.
That may sound obvious, but it is the period's main job.
Periods in abbreviations
The period has a second job: it marks an abbreviation. Many shortened words and terms end in a period, titles among them:
- Titles: Dr., Mr., Mrs., Prof.
- Degrees: M.D., Ph.D.
- Latin abbreviations: etc., cf., i.e., e.g.
British English often leaves out the period when an abbreviation ends with the last letter of the full word, as in Dr, Mr, and Mrs. American English keeps it.
If a sentence ends with an abbreviation that has a period, do not add a second period. The period of the abbreviation also ends the sentence.
Correct: I did the shopping, the cooking, the dishes, etc. Now it's your turn.
Incorrect: I did the shopping, the cooking, the dishes, etc.. Now it's your turn.
A question mark is different: it still follows the abbreviation, as in "Did you buy eggs, milk, bread, etc.?"
When a sentence does not end with a period
Of course, the rule has exceptions. Some sentences end with another punctuation mark:
- A question ends with a question mark (?).
- An exclamation ends with an exclamation mark (!).
- A sentence that ends with a quotation keeps its period inside the closing quotation mark in American English: She said, "I'm ready." British English puts it inside only when it belongs to the quoted words. The post on punctuation inside or outside quotation marks explains the details.
In informal writing and in fiction, a sentence can also end with an ellipsis, three dots that show hesitation or that something is left unsaid.