Dashes  

There are two similar but distinct punctuation marks called dashes: the en dash ( – ) and the em dash ( — ). In appearance, an en dash is slightly longer than a hyphen ( - ), approximately the width of a capital N, while an em dash is slightly longer than an en dash, approximately the width of a capital M (hence their names).

When we refer to dashes, we are usually referring to em dashes, as they are the more common punctuation mark of the two. However, it’s important to know the different ways that each mark is used.

En dashes (sometimes referred to as n-dashes or en rules) are the preferred punctuation to indicate a range or the result of a contest or vote, or to establish a connection or conflict between two people or things. (The en dash also has an optional use when forming certain compound words, which we’ll look at a little later.)

We do not use a space between the en dash and the two elements it is connecting.

The most common use of the en dash is to connect two numbers, dates, or times to indicate a range that spans these figures. We can think of the en dash as representing the words to or through when it is used in this way. For example:

Note that when the items in the range contain multiple words, we place the en dash between the last word of the first element and the first word of the second element, as in:

If the first part of the range includes an abbreviation marked with a period, the en dash appears directly alongside it—we still do not put a space between the two. For example:

Note that some style guides do not recommend using an en dash when a range is introduced by a word like from or between. In very formal or professional writing, consult your school’s or employer’s style guide; otherwise, it is largely a matter of personal preference.

When we write the score of a competition, such as a sporting event or a vote, we use an en dash between the two numbers. Again, think of the en dash as standing in for the word to in this case. For example:

We can also use an en dash when we want to express a direct connection between two people, things, or places. This is different from simply joining them as a compound modifier to describe the same noun (which we would use a hyphen for). This use can be a bit trickier to understand, so let’s look at some examples:

Even though each pairing is modifying the noun or nouns that follow it (trade deal, divide, flight, match), the en dash in each is expressing an explicit connection between the two elements that a hyphen would not be able to demonstrate. If we were to use a hyphen instead of an en dash, it would combine the two elements in each pair into a single modifying element, thus confusing the meaning of each sentence. For instance, “Mexico-U.S. trade deal” suggests Mexico and the United States as a single entity, rather than two separate parties engaged in the same trade deal. If we want to preserve the intended meaning, we must use an en dash.

We sometimes use an en dash when referencing a technical element that appears elsewhere in the text (as in an appendix). For instance:

While we typically only use hyphens to form compound words, some style guides recommend using an en dash instead if we are joining an existing compound (whether open or hyphenated) with another word. For example:

Other style guides only suggest using the en dash when forming compounds with multiple-word proper nouns and adjectives, in which case our second and fourth examples above would only use hyphens.

Either way, the use of en dashes rather than hyphens to form compounds is largely a matter of personal preference for writers; unless your school’s or employer’s in-house style guide provides specific guidelines, just use whichever form looks best to you and be consistent.

Because they are so similar in appearance (and because there is no dedicated “en dash” button on a keyboard), many writers tend to simply use hyphens in place of en dashes in all cases for the sake of ease.

Let’s look at some of our examples from above, this time using hyphens instead of en dashes:

While there is not much difference between the two forms in their appearance, the extra length of the en dash is usually preferred because it helps to specify its exact function within the context. If there are several hyphens that perform different functions in the same sentence or paragraph, the text may be difficult or confusing to read.

Em dashes (also known as m-dashes or em rules) are primarily used to indicate parenthetical information. In this way, they act as more emphatic alternatives to commas and parentheses. While parentheses and commas are used to include parenthetical information more naturally and subtly in a sentence, a dash creates a more forceful break in the text that serves to emphasize and highlight such information.

In addition, em dashes can be used instead of colons and semicolons in less formal writing, and they can also be used to represent missing or omitted text and to indicate a break in dialogue.

In addition to many other functions, commas are often used to enclose parenthetical information, such as absolute phrases, appositives, relative clauses, and interjections. It is an understated punctuation mark that does not draw the reader’s attention away from the rest of the sentence, instead weaving the parenthetical statement into the natural flow of the sentence. If we want to emphasize the information, though, we can instead use em dashes, which break the flow of the sentence and force the reader to pay closer attention. (Em dashes are also useful if the parenthetical statement contains internal commas that might cause confusion.)

Let’s look at different types of parenthetical writing and examine when it is—or is not—appropriate to use an em dash in place of a comma.

An absolute phrase (sometimes known as an absolute construction) is a grammatically independent group of words (usually, but not always, a noun phrase and a past or present participle) that adds a parenthetical commentary on the rest of the sentence.

Absolute phrases can appear at the beginning, middle, or end of a sentence. For the most part, we would use a comma with absolute phrases that appear at the beginning or end of a sentence, because an em dash would interrupt the flow of the sentence too dramatically (and might cause confusion as a result).

But for absolute phrases that appear in the middle of a sentence, em dashes can sometimes be useful to add forceful emphasis to the parenthetical statement. However, we must be careful not to use em dashes when they might make the sentence awkward or confusing to read.

For example:

If you are in doubt as to whether dashes will be appropriate to use with an absolute phrase, it is safer just to use commas.

An appositive is a proper noun or a noun phrase that serves to describe or rename another noun (or pronoun). Appositives can either be restrictive, meaning they are essential to the meaning of the sentence, or non-restrictive, meaning they are parenthetical and thus nonessential to the meaning of the sentence. Only non-restrictive appositives can be set apart by commas or em dashes.

Like absolute phrases, appositives can appear anywhere in a sentence. While we would normally only substitute commas with em dashes for appositives appearing in the middle of a sentence, we can use em dashes for appositives at the end of a sentence if we want to emphasize the added information. For example:

Relative clauses (also known as adjective clauses or adjectival clauses) are dependent clauses that provide descriptive information about a noun or noun phrase. Relative clauses are introduced by either a relative pronoun (who, whom, whose, which, and that) or a relative adverb (where, when, and why).

Like appositives, relative clauses provide information that is either essential (restrictive) or nonessential (non-restrictive) to the completeness of the sentence; only non-restrictive relative clauses are set apart by commas or em dashes. For example:

An interjection, also known as an exclamation, is a word, phrase, or sound used to convey an emotion such as surprise, excitement, happiness, or anger. Interjections can stand alone as minor sentences, punctuated with a period, exclamation point, or question mark.

However, since interjections are not “proper” sentences, some writers prefer to attach them to a complete sentence using a comma or, if more emphasis is desired, an em dash. (Ultimately, it is up to preference, but note that this use of the em dash is very informal.)

For example:

We can also use other phrases or clauses parenthetically to provide supporting information or commentary on the rest of the sentence. Again, how we set these apart from the rest of the text depends on the level of emphasis we want to add to them. In some cases, an em dash is actually preferable to a comma. For example:

Note that in each of the examples above, we could have used parentheses instead of commas or em dashes to indicate the parenthetical information.

Parentheses always travel in pairs of two, no matter where they appear in a sentence. Because they are self-contained, there is generally no restriction as to what information can be included within them, so long as it is grammatically independent of the rest of the sentence.

Like commas, parentheses can often be replaced by em dashes in a sentence if we want (or ought) to draw more attention to the information within them. Just be aware that em dashes are considered much less formal than parentheses, so they should be avoided when writing professional or academic material.

While we always use two parentheses, we only use one em dash if it is used at the beginning or end of a sentence. Additionally, a set of parentheses will operate in conjunction with surrounding commas, while em dashes will replace the commas altogether.

Let’s look at some examples:

Note that em dashes should not be substituted for parentheses in more technical, specialized uses (such as enclosing numbers or letters in a list, area codes of telephone numbers, or a person’s birth year). For more information on these types of uses, see the section on Parentheses.

In less formal writing, we can often substitute an em dash for a colon if we want to quickly indicate or emphasize a list or clarifying information. Just remember that we can only use a colon after an independent clause—that is, one that can stand on its own as a complete sentence—and we must apply the same rule if we are using an em dash instead.

For example:

We sometimes capitalize the first word that follows a colon (see the article on Colons for more on this topic), but we should never do so after an em dash. For instance:

An em dash can also be used in place of a semicolon when joining two independent clauses to form a compound sentence. This can help achieve a less formal or stuffy tone, and it is also a useful way of adding emphasis to the sentence. For example:

In addition to replacing other types of punctuation, the em dash can also be used in two specific technical ways: representing missing text and indicating an interruption in dialogue.

Occasionally, dashes can be used to represent words or parts of words that are omitted from a sentence. These can be intentional omissions, as for censorship purposes, or because the missing text is unknown. If only a part of a word is missing, we represent it with two em dashes in a row; if an entire word is omitted, it is represented with two or three em dashes (depending on the writer’s preference). Unlike in other uses for the em dash, other punctuation in the sentence (such as commas) will appear as usual.

For example:

We can also use the em dash to signify when someone has been interrupted while talking or thinking. We can use either a single or a double em dash to this effect; it’s entirely up to personal preference (just be sure to be consistent). For example:

Conventionally, we do not put spaces around em dashes. However, many writers (especially journalists and online writers) prefer to include a space on either side of a dash to aid readability. For example:

Regardless of convention, whether or not to use spaces generally comes down to personal preference; just be sure to check whether the style guide of your school or employer specifically requires that they be included or omitted.

It is quite common to see writers use hyphens instead of em dashes, due to the speed and ease with which a hyphen can typed. However, this should be avoided, as having hyphens performing too many functions in a sentence can lead to some very confusing reading.

If you need to use a hyphen instead of a dash—for instance, if you are using a typewriter or the keyboard on a mobile device, and you are unable to form a true em dash—then you should use two hyphens in a row. (Do not just use a single hyphen, as it might look like you’re creating a compound word.) For example:

It’s also not uncommon to see an en dash used instead of an em dash, especially in published writing. Again, this is not the preferred mark according to the majority of style guides, but it is not necessarily incorrect. If en dashes are used, they should be surrounded by spaces to avoid making the words appear too close together. For instance: