Punctuation series: Hyphens and dashes

Punctuation is the set of marks that give depth, pace and force to our words. Much like the dynamics in written music, punctuation gives the reader the extra information they need to secure the tone of the text and deepen their understanding. The Punctuation series is a collection of articles detailing the use of particular punctuation types, to help you use these precision tools to their fullest advantage.

A horizontal line in the middle of a string of text gives the reader a bridge across a shift in ideas.

They can speed up a sentence by stringing together quick-moving thoughts—creating speed—breaking flow—joining randoms—wow, many ideas—so speed! And they can be used in pairs to set apart a bit of text of text—a totally different bit—before jumping back to the main string.

There's other places a wee horizontal line links ideas together: in spans of numbers, in compound words, and, if you're a bit clever, in list items that seem to dangle until you resolve them all with a secure ending.

There are some pitfalls to look out for, but a horizontal line can be an excellent punctuation tool.

What's the difference?

Before we go any further, let's clear this up: there are different types of lines. Know your tools.

• Hyphen
• En dash
• Em dash

I hear you grumbling in the back there. What's the point of having three types of line? Just use a hyphen and whatever, move on with your life. Well, you can use a screwdriver handle in place of a hammer, but it doesn't do as good a job. Each of these tiny horizontal lines is designed to communicate a particular kind of span between concepts, and that is somewhat reflected in their size. That, my argumentative straw-friend, is why we have three types of line.

Now, let's have a quick definition spree:

• Hyphen (-): The hyphen is the shortest of the dash family. Thus, it's used to show the tiniest gap between concepts. For example, between syl-la-bles within one word, or to fuse related words together to make unambiguous modifiers, like "little-recognised greyhounds" or "three-year-old ponies". Hyphens are also the little tykes you use to indicate that a word has broken over a line, such as:

Microphones will be att-
ached to all the ponies
in attendance.

• En dash (–): The en dash is the second longest of the dash family. Called the en dash because it is historically as wide as the letter N (or sometimes the letter n) in whatever typeface you're using. This varies with the style of the typeface, but it's a good rule of thumb. The en dash is used for relationships and spans. For example:

  • This is a key element in maintaining pony–rider harmony. (relationship)
  • Ponies were introduced as messengers during the 1981–84 Battle for Wall Street. (span)

• Em dash (—): The em dash is the longest of the dashes, twice as long as the en dash, and generally as wide as the letter M or m in whatever typeface you're using. As the longest of the dashes, em dashes can span bigger breaks in concept. They can set aside parenthetical remarks, or even flag a sudden break of concept altogether:

  • The notion—which I know you've heard before—of pony liberation is an appealing one.

  • "But what about the—"
    "The ponies?"
    "— the ponies!"

Here's your guiding principle, wandering punctuator: the bigger the break in idea, the bigger a line you'll need to cross it. Just breaking a word into its sounds, not fiddling with its meaning? The hyphen is all that's nec-ess-ar-y here, my friend. Breaking a sentence to add an extra remark—that might be otherwise excluded—to add some explanation? That's an em dash right there.

It's a pretty easy rule to apply when you break it down like that, but there's a couple of gotchas to keep an eye on.

What are you trying to do?

Keep in mind, the bigger the jump you're helping your reader cross, the bigger the line you'll need.

When to use an em-dash

Extra thoughts

If you're putting a whole new thought, like an explanation or an interjection, within a sentence or a string, then set it aside with an em dash. A whole new idea is a big span to cross.

• Most ponies—there's one now!—will be delighted to give you a ride.
• Don't ever underestimate the pony—many people do, to their detriment.

Sudden interruptions

If you're breaking off a line of thought completely (most commonly seen in dialogue), then you'll need an em dash. What bigger gap to cross than the premature termination of a thought?

It's worth considering that, in this situation, you could also use an ellipsis, but it depends what effect you're going for. An ellipsis is a slow trailing off, perhaps to reflect a growing realisation in the speaker's mind, whereas an em dash is an abrupt cessation, usually to indicate the speaker has been acted upon by an outside force.

When to use an en-dash

The en dash is used for crossing moderate gaps: two similar things in a common relationship or a span in times, dates, sizes, and other numeric measurements.

Relationships

If you're showing a relationship between things, your reader has a short mental gap to cross: span it with an en dash, our middle-sized dash.

• The Patagonia–France treaty preserved pony trade between the two countries.
• The London–New York flight exhausted the ponies.

Dates and numbers

Similarly, if you're spanning a date or numeric range, then you should invite your en dash along for the party:

• The 1818–25 Reign of the Pony Queen was a glorious time.
• Ponies suit the 13–17 age group.
• You'll find this data in "Hind's Book of Ponydom" (pp39–287).

When to use a hyphen

Stringing syllables (syl-lab-if-i-ca-ti-on)

One of the shortest spans you'll ever need to cross with a horizontal line is the span between syllables. String them together with the shortest dash at your disposal, a hyphen.

Over a line break

If you have a word that unfortunately hits the end of the line and runs out of space, keep it together with a hyphen. You will very, very, very rarely need to do this by hand. Word processing software will usually identify places a hyphen could be inserted in a word in order to allow a line break. As a rule, try to break at a syllable join, and keep more than a few letters on each line (don't break between the second-last and last letters, for example).

Compound words

If you're joining words together to make a new word that you'll then use to adjust another word, then hyphens are your jam. Sound fiddly? Nope, you do it all the time. They're called compound modifiers, and hyphens will stop you accidentally building confusing or ambiguous compounds.

• Four-year-old ponies: if you leave out those hyphens, especially the one between "four" and "year", you suddenly have an ambiguous phrase. Do we have four ponies, each a year old? Or do we have a unnumbered collection of ponies, all four years old?

• Man-eating pony: again, leaving out that hyphen creates an ambiguous string. Do we have some dude chomping down on ponies like a barbaric Pacman or do we have an ominous development in Nature's war on humankind?

But. There's a big ol' caveat you should know about here. Now you've learned how to build compound words with hyphens, you'll be tempted to scatter them around like confetti at a pony party. The point of the hyphens here are to prevent ambiguity. If your compound is unambiguous, you usually don't need to throw in a hyphen:

• "little celebrated breeds of ponies" could mean either "celebrated breeds of ponies that are small", or "breeds of ponies that are infrequently celebrated": to disambiguate, hyphenate "little-celebrated". In this example, the compound modifier is an adjective-adjective combo.

However, if your compound word is an adverb-adjective combo, there's far less room for ambiguity: the adverb is modifying the adjective, and there's no disputing it.

• "frequently celebrated" is a compound that is adverb-adjective. No hyphen needed there!

And, finally: you don't need to hyphenate a compound that comes after the noun. You might have a "well-endowed pony", but you'll find that the "pony is well endowed". No hyphen needed if the compound follows the noun.

Advanced use

Feeling pretty confident with the dash family now? Well, sharpen your pencil and boil your ink: you're ready for advanced use. Proceed with wisdom, punctuator.

Building up your words

I already discussed the use of hyphens in joining words to produce compound modifiers: words made of groups of words used to adjust other words.

Well, let's say you're creating a compound modifier out of words that have already been compounded. If that's the case, compound your compounds with an en dash! If you have the compound modifiers "private-school" and "public-school", and you need to compound them into the adjective to describe a particular debate, you would compound them using an en dash: "private-school–public-school debate".

If you're tempted to elevate even further and compound two en dash-compounded compounds with an em dash as a joiner, then you should probably have your keyboard taken off you for a while and be sent out for some fresh air.

Dangling dashes

Let's say you're investigating a herd of ponies, whose ancestors go back centuries. Some go back to the seventeenth century. Some have ancestors that go back to the sixteenth century. Some have ancestors that only go as far as the twentieth century. The point is, this herd of sixteenth-, seventeenth- and twentieth-century lineages is a beautiful (if complex) one.

Whoa, see what I did there?

That's your suspended hyphen. Used to tighten up a sentence which would otherwise be wandering and wordy, the hyphen at the end of the first couple of words indicates that they're compound modifiers, and that the remainder of that compound will be along shortly. It is possible to use the suspended hyphen in such a way that the first element in the list uses the full compound, and subsequent items use the severed compound, but it's a bit uncommon, and generally used when the common element of the compound comes first. You might use it in something like "The post-war, -Freudian, -civil rights, and -feminist era was a beautiful and rich period."

Conclusion

An excellent rule of thumb is to consider the distance between concepts you're trying to bridge: let that guide the length of the horizontal line you need.

Of course, if you're working to a style guide, you should always default to its recommendations. Happy punctuating!