A dash (—) is a punctuation mark used to set off an idea within a sentence and may be used alone or in pairs. Dashes interrupt a thought in a more dramatic way than a phrase enclosed in commas, but less theatrically than parentheses.
To form a dash, type two hyphens—without a space before, after, or between them—and your word processor will convert them to a dash. You make a dash by hitting the hyphen key twice. The hyphen key is next to the +/= key on your keyboard (the same key with the underscore _ ). Some Word programs will automatically join your hyphens together to make a dash, and some will leave the space. Either way is fine!
Dashes can be placed at the beginning, middle, or end of a sentence, depending on what you want to emphasize:
- Teaching—the profession has always appealed to me.
- The idea of being a teacher—working with kids, summers off—has always appealed to me.
- I have always known what I want to be—a teacher.
Note: If you put a dash in the middle of your sentence, you need to place another dash at the end of the emphasized information (like parentheses!).
Use dashes thoughtfully and sparingly, or they may lose their effectiveness.
How should dashes be used?
- To provide further explanation, clarification, or a summary of the material that comes before the dash
- Cell phones, hand-held computers, and built-in TVs—each a possible distraction—can lead to a potentially dangerous situation if used while driving.
- To introduce a short list within a sentence
- The young woman took all of the necessary supplies—leash, pet carrier, and paperwork—to the shelter when she went to pick up her newly-adopted dog.
- To define a term
- Genocide—the systematic killing of a racial group—is an atrocity that has created black holes in history.
- To highlight information at the end of a sentence
- Childhood obesity has become a grave concern in many parts of the world—particularly during the last two decades.
- To indicate a change in tone
- She finally let down her guard—and cried like a baby—when the counselor urged her to let go of her pain.
Use a Dash after a Series or List of Appositives
When you introduce a long series or list of appositives before the subject and verb, you are placing high demands on the reader’s short-term memory. Therefore, use this pattern rarely and only for emphasis. This pattern is particularly appropriate in conclusions, when you are bringing together the major threads of your discussion or argument. Finally, you should place a summary word after the dash and preferably before the subject of the sentence, as indicated by the following examples. The most common summary words that writers use are all, those, this, each, what, none, such, these.
- Jealousy, lust, hate, greed–these are the raw emotions we will explore.
- Lying, stealing, cheating, committing adultery–which is the greatest sin?
- To struggle with meaning, to edit, to combine sentences–these activities are well known to the struggling writer.
- Wining and dining his friends, stroking people’s egos, maintaining a good appearance, and spending money–all were part of his scheme to gain influence.
Use Dashes When You Wish to Emphasize a Parenthetical Element
Commas are usually sufficient punctuation to set off parenthetical elements. In some instances, however, you can use a dash instead, especially if you want to make the insertion more noticeable:
- The building next to ours–the one with the all-cedar exterior–was engulfed in flames.
When you want to whisper rather than shout, you can place the modifiers inside parentheses:
- The secret I have to tell you (the one I’ve been hinting about) will surprise you.
Use Dashes to Embed a Series or List of Appositives
A single appositive or modifier can easily be set off from the rest of the sentence in commas, but you must use dashes when you insert a series of appositives or modifiers. After all, how else will the reader know when the series is over?
- The essential qualities of an effective writer–discipline, effort, inspiration–can be learned by regular writing.
- With the help of her assistant–a high-speed personal computer–she produced a delightful letter.
Use Dashes to Set off an Emphatic Repetition
You can emphasize an important point by placing a dash or comma at the end of the sentence and then repeating a key word or phrase:
- Hal is a computer, the ultimate computer.
- Mrs. Leavitt is a gambler, a compulsive gambler.
- He was disturbed by the warning–the warning that everyone else ignored.
- All rapists should be severely punished–punished in a way they will never forget.