Hyphens, En Dashes, and Em Dashes have been around for quite some time, but contemporary writers are not always sure how they should be used or what the difference is between them.
Are These Really That Different?
They are! Despite their having been around for a long time, many people today are not familiar with their use for one main reason: the typewriter.
Space limitations on the typewriter meant that not every character could be represented. Some characters had to do double duty:
- The numeral l was provided by the lowercase l
- The exclamation point ! was provided by the . and then backspacing to type ‘
- The en and em dashes were made by typing the hyphen – twice (- -) and three times (- – -)1I once knew someone who wanted to call her band “Em Dash and the Triple Proxy Hyphens”
But because there was only one – key on the keyboard, the differences in the usages of hyphens, en dashes, and em dashes were lost. Our modern computer keyboards still lack these symbols as separate characters, and although there are some workarounds (such as typing two hyphens in rapid succession to produce an em dash or using ALT codes), our general familiarity with these symbols and their use remains lacking.
Fortunately, we’re here to help.
Using Hyphens, En Dashes, and Em Dashes
The hyphen is used to join together two or more words that are being used as a modifier of another word.
- That was a well-cooked meal.
- The soldiers were equipped with high-caliber weapons.
- The house was buffeted by gale-force winds.
- The three-year-old boys sat in the corner and cried.2Note how this last example even resolves some ambiguity: it is clear that there are a number of boys, three years of age, sitting in the corner. If there were three boys a year old doing so, you could write The three year-old boys sat in the corner and cried.
You can even use hyphens when the combined words are being used in a predicate context, that is, on the other side of the verb to be:
- I like a meal that is well-cooked.
- The soldiers’ weapons were high-caliber.
- The hurricane winds were gale-force.
This is distinguished from contexts where the words are not modifying some other word:
- I hope we can find candidates who are of a high caliber.
Additionally, hyphens are used in combined surnames like Catherine Zeta-Jones and John Rhys-Davies, in telephone numbers (202-456-1212), and in ZIP codes, among others.
The key to understanding the hyphen is that it is linking words and numbers together to act as one. And this is what distinguishes the hyphen from the other punctuation marks here.
The En Dash
Of the three punctuation marks, the en dash is probably the least understood.
The en dash—so called because it is the width of a typesetter’s n—is used primarily to define relationships and ranges.
For example, when two scientists discover something, the use of their names together to describe their discovery is made with an en dash:
- The Watson–Crick [en dash] study revealed the double-helix [hyphen] nature of DNA.
- The Hale–Bopp comet was a spectacular site in the night sky.
Here, the en dash functions in place of and and highlights the relationship between the two names, e.g., that they are co-discoverors.
The en dash is used for directional connections as well:
- The north–south migration patterns of Canada geese have been studied for years.
- The Asia–Europe pipeline will bring needed fuel in the middle of a harsh European winter.
In such cases, the en dash is equivalent to the word to: north to south and Asia to Europe.
Finally, en dashes are used numerical and alphabetic ranges:
- The Big Book of Punctuation, pp. 78–95.
- The researchers discovered the particles had diameters of 55–100µ.
- The Encyclopedia of Punctuation and Abbreviations, Vol. I, A–E.
The Em Dash
The final punctuation mark to look at is the em dash—so called because it is the width of a typesetter’s em (m), twice the width of an en.
Whereas hyphens and en dashes are used to link words, em dashes are used to set them apart. Em dashes represent a break more significant than a comma but not as significant as a period.
Because of that, they can be used in a number of different contexts:
Em dashes can be used for parenthetical phrases instead of parentheses:
- My favorite toy—from the time I was a child—has always been Legos.
Em dashes come in particularly handy when there are already many commas in a sentence or when commas would not sufficiently set the parenthetical text apart:
- She traveled to Bozeman, Montana, and there, in the middle of the long, unpaved street—a street that had been left in its original dirt-road state—she saw the sheriff standing with a letter in his hand.
- Related research tracing the flow of carbon through tree roots revealed that the zone of influence of a tree or cluster of trees—the area across which they actively supply microbes and other tiny organisms with carbon-rich molecules—extends about 33 feet on average.3National Geographic, “Out of Sight,” September 2022, 98.
Here, the em dash can function almost like a colon or semicolon, creating a marked break or pause in the text. Unlike the colon or semicolon, however, the em dash has a way of focusing the reader’s eye on what comes after:
- The retreat marks a major embarrassment for Moscow, a day after it claimed swaths of eastern Ukraine as its own—in the face of widespread international condemnation.4Washington Post, “Russian troops leave key city,” October 2, 2022, A1.
- That leaves open the door to the lively and impressive tradition of Christian anarchism—for example, Dorothy Day’s Catholic Workers Movement.5Noam Chomsky, What Kind of Creatures Are We?, 65.
- He thinks the Blue Jays are going to win it all this year—I’m not so sure.
- There is one major problem with your idea—it stinks.
The use of em dashes is much more style-driven than rule-driven. In the examples above, the em dashes could have been replaced by commas, parentheses, colons, or semicolons where appropriate, but the use of the em dash has a way of setting off the text in ways those other punctuation marks cannot. The em dash creates the sensation of a much bigger break in the mind of a reader—much the same way that writing. with. periods. slows. the. reader. down. (Don’t do this is formal writing!)
So, there you have it—your quick guide to the use of hyphens, en dashes, and em dashes. Of course, there are many other rules and usage guidelines to these marks than those I have shared with you here, but these should give you some sense of the differentiation between them.
With this information, you’ll be a better-informed writer 80–90% of the time—at least, that’s the hope.