There are only three punctuation marks with which you can end a sentence: a full stop (.), a question mark (?), and an exclamation mark (!). These punctuation marks separate sentences. All the others – commas, dashes, colons and semi-colons are used to connect phrases or clauses within a sentence.
Full stops
The first and most common ending is the full stop, also known as a period:
The man arrived. He sat down.
A full stop nearly always follows a complete sentence, with a subject, a verb and an object:
The man (subject) was reading (verb) a newspaper (object).
Occasionally it can be used after an incomplete sentence, or even a single word, for emphasis:
This is the end. Finito.
This is a very strong effect, and while common in casual speech, should be used very sparingly in writing.
Sometimes people – even those for whom English is their first language – connect complete sentences with a comma:
The man went into town, he bought a newspaper.
This is OK in some languages (German, for example), but it is not correct English. These are two separate sentences and must either be joined by a conjunction such as and, or separated by a full stop:
The man went into town. He bought a newspaper.
When a full stop is part of a quotation, people often wonder if it should go inside or outside the quotation marks. If a quote is a whole sentence, with a subject, a verb and an object, then the full stop should come before the closing quote:
Smith and Eriksson (2003) argue that “the molecular structures involved in this process are extremely complex.”
If the quote is only part of a sentence, the full stop comes after the closing quote.
Smith and Eriksson (2003) describe the molecular structures as “extremely complex”.
One last point. Many people type a double space after a full stop. This is a hangover from the days of manual typewriters and should be avoided.
Question marks
If a sentenceposes a question, it must end in a question mark:
What is your name?
What were the long-term consequences of Frederick the Great’s foreign policy?
How do I get to the center of town from here?
Sometimes, for dramatic effect, people will phrase a statement as a question. This is known as a rhetorical question, and because, grammatically, it is still a questions, it still needs a question mark, even though the speaker doesn’t expect an answer:
Who knows where the time goes?
Who would have thought it would come to this?
Conversely, you should not use a question mark after an indirect or reported question:
She wondered what time the train would get in.
He asked a passer-by what was going on.
Requests or instructions are sometimes phrased as questions out of politeness. Because these are not really questions, they do not take a question mark:
Could you please send me your CV.
Would all passengers please form an orderly queue.
Exclamation marks
An exclamation mark is usedto indicate a moment of drama or to show strong feeling. Itis the written equivalent of raising your voice. The exclamation mark is therefore most often used in quoted speech, to indicate just that:
“Be careful!” she warned.
Exclamation marks are sometimes used in newspaper headlines for dramatic effect;journalists call them “screamers”:
Stock market crashes!
Do not overuse exclamation marks; they can appear sensationalistic, naïve or amateurish. In formal contexts such as a business letter or academic paper, it’s better not to use them at all. Ever!
