Here are my guidelines on how to use some much-neglected horizontal lines that are a great joy to contemplate — and even use — when understood and respected. (I’ve tried not to make them too tedious, but they are rather long. ????) These only apply to formal writing, but stay tuned for the updated chapters in my punctuation guide!
To summarize: A hyphen (the shortest horizontal line) connects words; an en dash (medium length) links words that are separate but related; and an em dash (or long dash) is a stop, like a comma or colon.
Hyphens
A hyphen (-) is used to link two or more closely related words that can’t be written as one word, such as forest-green and strange-smelling. Basically, a hyphen is half a space. Hyphens are often confused with dashes, which have different purposes listed below. To clarify: the hyphen is the shortest horizontal line, which you get by simply tapping the key with a picture of it. It’s often called and used as a dash, but it’s not. For information on dashes, read the next two to four sections.
And be careful — hyphens are extremely slippery creatures, and while they seem insignificant, THEY ARE NOT. Proceed with caution.
Compound modifiers. Hyphens are used in compound modifiers, which are multiple words that together act like an adjective: strange-seeming, sky-colored, hyphen-or-dash dilemma, twenty-year anniversary, two-inch-long potato, sign-up (or log-in) sheet. These are often a noun followed by a verbal adjective (such as seeming or covered). Even longer phrases can be hyphenated to become adjectives: She gave me a why-on-Earth-are-you-hyphenating-that stare. Also, two adjectives that are merged into one (such as blue-green, and crazy-awesome, though crazy here is more of an adverb) are hyphenated.And now, I’ll point out that sometimes the hyphen isn’t always necessary (high school teacher), and whether you use it is a matter of style.
Punctuation pitfall. Only hyphenate these words when they’re serving as adjectives that come before a noun. So the potato isn’t two-inches-long, and while sign-up and log-in keep their hyphens as nouns (or are written as one word), as verbs they are not, and never should be, one word. Perhaps they will be some day, but they are not now. So I will sign up, and I will not sign-up or signup. After all, you signed up, not signupped.
Punctuation pitfall 2. An adverb modifying an adjective is also separate; it’s strangely mesmerizing when someone accidentally writes strangely-mesmerizing. (To me, anyway.) Sometimes, though, it’s necessary for clarification when the adverb could also be an adjective: deadly-serious, an extra-green apple, one more-cautious squirrel. Deadly is both an adjective and an adverb, and extra and more could be misinterpreted.
Nouns. Some compound nouns have hyphens, though many times the hyphen is optional. This is the most random, unpredictable use of hyphens, so I’ll list some: daughter-in-law, six-pack, etc. Here the hyphens are optional: water-bottle, ink-well, apple-tree, etc.
Affixes. A hyphen can also be used to add prefixes or suffixes to words: pre-reupholstering, quasi-editor, potato-wise, lexicostatistics-y, carrot-esque, etc. (Sometimes such things, such as tomatoey and starefest, can be written as one word; it’s a matter of opinion.)
Pronunciation. Also, they can be used to avoid confusion in pronunciation: Co-op is spelled with a hyphen to distinguish it from coop, but cooperate is unambiguous, so the hyphen is unnecessary. Hyphens separate vowels (co-op, de-ice, but not usually reentered) and triple consonants (bell-like), though these are rare. A diaeresis — which is the two dots in naïve — can be (but almost never is) used on the second vowel instead. Again, there’s no one correct way: Pre-empt can also be spelled as preempt, or (very occasionally) preëmpt.
Syllabication. When splitting a word at the end of a line of text, put a hyphen at the end of the first line. And please split the word between syllables. Which letters belong to which syllable? I know, it’s very confusing, but a dictionary should tell you. So, some examples are leg(-/)er-/de(-/)main, ma(-/)jus-/cule, dic(-/)tion-/ar(-/)y, sil-/ent. With compound words and those with added affixes, split it in the logical place: straw-/berry, over-/whelmed, quag-/mire, pains-/taking, see-/ing. If the word already has a hyphen, split it at the hyphen: ever-/unchanging. (That only has a hyphen before a noun.) Speaking of which, usage isn’t, so this advice won’t last forever. But that is not the point.
Suspended hyphens. When there are two words connected to a single word (or vice versa), punctuate the sentence as follows: There’s a cloth- and tarp-covered cage in the Reptile Room. Or the other way around: potato-shaped and -colored. They can occasionally be used in unhyphenated words: him- or herself. This is the only time a space is used next to a hyphen, and there should never be a space on both sides. (Unless it’s representing an em dash, but then you should find an em-dash character or, if you can’t, use two hyphens.)
Numbers. Hyphenate two-digit numbers: ninety-nine, fifty-seven, etc. Hyphens are also used in phone numbers, various cataloguing numbers, and so on. For more information, consult the Chicago Manual of Style.
Names. Some last names, as I’m sure you know, are hyphenated. Thankfully, it’s straightforward: People can tell you if their names have hyphens.
Emoticons. A hyphen can also be the now-obsolete nose in the face emoticons: :-), :-(, :-D, etc.
If you’re wondering whether or not to hyphenate something, look it up in a fairly recent dictionary, on a reputable website, or in a trustworthy style manual. Like I said, though, hyphens are slippery creatures, and people will probably disagree. Ultimately, it is up to you (but please don’t neglect the hyphens). Notice, though, that while hyphens have a multitude of uses, there are also many things they don’t do. They are taking over THE ENTIRE WORLD by being overused as dashes (and being called dashes, too), so if you are about to use one, please ask, is this hyphen connecting words? Or is this like a semicolon or comma? If it’s the latter, use an em dash (third paragraph).
En Dashes
An en dash (–) is used in American English to link two words that are not as closely related. It is longer than a hyphen and shorter than an em dash. To type one, press option-hyphen on a keyboard or hold down the hyphen key and choose the shorter dash on an on-screen keyboard. There is never a space next to an en dash in American usage, but in British English an en dash with spaces next to it is used instead of an em dash.
Numbers and time. It often replaces the word to. Examples: 2:00 p.m.–5:00 p.m., 2017–19,1914–2015, 3–5 apples, May–October. (It’s really different from a hyphen! Isn’t that amazing?)
Phrases. En dashes are also used when a compound modifier has a multi-word (did you see that? A real live hyphen!) phrase as part of it: swimming pool–sized, an ice cream–flavored cupcake. With a hyphen, the word flavored would (technically) only be connected to cream. In reality, a hyphen would be fine, but an en dash is more accurate. Do the same thing when connecting an affix to a phrase: time travel–ish. You can also use one to add an affix to a proper noun; hyphens can also serve this purpose, but choose one and stick with it — consistency is important. Anyway, it will look like this: Alice in Wonderland–related, pre–Harry Potter, post–Renaissance.
More modifiers. An en dash is used in a compound modifier where a hyphen would sound strange: squirrel–human translator, Potatoville–Taterwald trade agreements, etc. Again, hyphens work, but I recommend an en dash where the adjective can’t stand alone — squirrel-human out of context would be a weird word, and you can’t describe a translator as being squirrel-human. However, a stretch of sidewalk can be leaf-covered, so leaf-covered functions as a normal hyphenated adjective.
Hyphenated compounds. Also, I use an en dash to connect an affix or a word to one that’s already hyphenated: pre–middle-grade, open-door–magic idea, etc. — though I’ll admit the latter is not the best phrasing. Everyone else uses a hyphen, though, since it’s not ambiguous.
You’re probably wondering, does anyone actually use en dashes? Not informally, but do some punctuation sleuthing the next time you read a published book. En dashes are rare, but they exist.
Em Dashes
An em dash (—), also known as a long dash or simply a dash, is a stop: Like a comma, semicolon, colon, ellipsis, and parenthesis, it separates clauses and occasionally marks pauses in speech. Note that in British English an en dash with a space on either side is used instead of an em dash. To type one, press option-shift-hyphen on a keyboard or, on an on-screen keyboard, hold down the hyphen key and choose the longer dash. Two hyphens can be used in place of an em dash informally and in a great emergency.
It is quick — dramatic — marks interruptions and asides — but it is an extremely versatile punctuation mark, which makes it easy to overuse. Be warned. It can be used in place of a comma, semicolon, colon, parenthesis, or bullet point, though it’s less formal. It also signifies a break in thought, in narrative, or in dialogue.
Spaces? Some people (myself included) use a space on either side unless there’s a quotation mark next to it, like this:
Potay replied, “Dragon–time machine connections are —”
“— None of the audience’s business,” Ol’ Tater declared.
But people don’t always use a space: Just one—last—potato! If you don’t, then use a single space when one sentence is cut off by another: But I— Why don’t I remind you of a potato?
Used like a comma, generally for dramatic effect. You can also use one where you normally wouldn’t use a comma. The effect is the same. The potato was there — and then it disappeared. They were there — interestingly. Despite all the warnings, all the perils — they still built time machines.
Used like a semicolon (or colon). Here it separates two independent clauses (phrases that could stand alone as grammatically complete sentences). Em dashes are easily overused — they are very convenient. I don’t know — I think so.
Used like a colon. In this case it elaborates on items in a list. Food — enough for two days. Water — it’ll last until we find some more. Duck Tape — almost a full roll. Books — oh, no. Only ten. Em dashes work well in this case, but colons are made for this purpose, and em dashes are usurping it.
Used like parentheses. Of course, this is much more emphatic. This punctuation still separates a detail from the rest of the sentence, but it does not imply that it’s not important. Where you lower your voice for parentheses, you raise it for dashes. Of all the books in the reading room — there were at least three hundred — the plain one with the pale green linen binding had been read the most.
Interpolation, interjections, and asides. When you interrupt yourself, this is where the em dash shines.There was a hyphen — how do you use those things, anyway? — in a word that didn’t exist. I saw a beetle — eek! — who has since fled. The meeting was on Thursday — which is weird — but it was successful anyway.
Break in thought. Same as above, except there’s one em dash instead of two. The Associated Press Guide to Punctuation says, “People may laugh at the grimly limited ampersand, but nobody laughs at the apostrophe. One of its main jobs is” — oh, I can’t spoil it for you! I’ll let you read it yourself.
I think if we multiply it by the square root of — look! A real unicorn!
If the speaker is trailing off instead of stopping abruptly, though, use an ellipsis: I think if we multiply it by the square root of . . . Can you get me a calculator?
Interruptions. Use an em dash at the end of the interrupted sentence:Mr. Anwhistle told them, “Inside the sugar bowl, there resides —”
“The cave is infested with Medusoid Mycelium, so take horseradish,” Fernald said abruptly.
If the second speaker picks up the first speaker’s sentence, use a dash at the beginning of the second sentence as well: Potay replied, “Dragon–time machine connections are —”
“— None of the audience’s business,” Ol’ Tater declared.
Stammering. In dialogue, when speakers are stuttering or are out of breath for some reason or another:
“I — I — I — Apologies, sir!”
“There — was — a — dragon,” Hazel panted. “Just — outran it.”
Attributions. You can attribute quotations using an em dash before the author’s name:
“And this our life, exempt from public haunt,
Finds tongues in trees, books in the running brooks,
Sermons in stones and good in every thing.
I would not change it.”
— William Shakespeare, As You Like It
Using em dashes is not the only way to attribute quotations but is used in epigraphs and stand-alone quotations. In a paragraph, simply mention the author — as Shakespeare said — or use parentheses: “. . . I would not change it” (William Shakespeare, As You Like It)
Signatures. An em dash can be used in the same way at the end of a message, but isn’t necessary:
Yes, that is correct. See you soon!
— Hazel
The em dash is unnecessary and should probably not be used after a phrase like regards, best wishes, etc. Some people use tildes (~) or hyphens for the two above, but I don’t think that’s correct (yet).
Dialogue and action. Interject an action into a line of dialogue when the speaker does not pause, like this: “I have Duck Tape but” — she tossed him the roll — “no parachute.” But if she does pause: “I have Duck Tape,” she said, appraising the roll, “and I think I can make a parachute.”
Double punctuation. Pairing other punctuation marks with em dashes is rarely necessary — you can probably just use an em dash and be done with it. However, there are times when an em dash followed by an exclamation point, question mark, or ellipsis conveys what you want to convey: “There was a dragon —?” “Obviously —!” “I suppose — . . .” Use a space between an em dash and an ellipsis, but not a question mark, exclamation point, comma, or quotation mark. (This is because em dashes and ellipses automatically come with spaces.) Also, there are times in dialogue when a comma can be used after the dash:
“But time machines are —,” an audience member objected.
“And dragons —,” another said.
“I’m potatoey enough to know —,” a third exclaimed.
Ol’ Tater refused.
Some people use commas like this; others just use the dash:
“But time machines are —” an audience member objected.
“And dragons —” another said.
“I’m potatoey enough to know —” a third exclaimed.
Ol’ Tater refused.
And yet others only use the comma if the quotation is a grammatically complete sentence, which would make it look like this:
“But time machines are —” an audience member objected.
“And dragons —” another said.
“I’m potatoey enough to know —,” a third exclaimed.
Ol’ Tater refused.
All of these are correct. Usually, though, there’s no need to pair a comma and a dash: You can, but needn’t, write Also, — never mind.
And thus you have met the em dash.
Other Horizontal Lines
Two-em dash. A two-em dash (⸺) — some people just use an em dash — is used in place of an omission. To get one, use a character-finding tool or copy and paste one from the internet. Some examples of its use are 20⸺ when you don’t want to name the year, or A City of ⸺ and Water if you don’t remember a word in a book title. It’s also used in place of words and names (or letters in them) you don’t want to say. In a quotation, use an ellipsis to mark omission, and in contractions, use an apostrophe.
Three-em dash. A three-em dash (⸻) is even more obscure. Again, use some sort of tool or copy and paste the character. It’s used in bibliographies to indicate that a book was written and published by the same people as the previous:
11 Quests, Barnaby Quirk, Blazing Things
⸻Everything League
You never know when you might write a long bibliography, right?
Minus sign. A minus sign (−), which I’m sure you know how to use, is slightly larger than an en dash and has a different Unicode character. You can get it the same way as a two-em or three-em dash. Sadly, most people just use a hyphen.
Underscore. And an underscore (_) is its own entity, used for programming and online usernames. On a keyboard, it’s shift-hyphen, and on an on-screen keyboard, it has its own key in the punctuation section.
And all the rest. Wow, there are a lot of horizontal lines in the world! To read about them, follow this link: https://en.m.wikipedia.org/wiki/Dash#Horizontal_bar
Notes
• I do not know everything (as you may have guessed), so if there are any correct usages I missed, any typos, any incorrect information, anything that was confusing, etc., please let me know so I can fix it. I want this to be comprehensive, and I can’t do that alone. (Plus, you get to correct a grammar nerd on her grammar! Is there anything more fun than that?)
• To learn how to type these characters, follow this link: http://www.techtoolsforwriters.com/how-to-create-an-em-dash/
• The two-em dash, three-em dash, and minus sign are not easily accessible; however, they exist. At least for now (nooooooo!). If you try to copy and paste one but it doesn’t work (and if you bothered to do this, you have my eternal gratitude), the font you’re using may not have them.
• I’ve tried to include all correct usages, but please let me know if I missed anything. Also, I use American style rules, so usage may be different in British English. Please consult references for the style you use.
• In case you were wondering, an en is a unit of measure equal to the width of a capital letter N. Ems are the same except they’re as wide as the letter M, also capitalized. The corresponding dashes are the same length.
• Most importantly, my grammar and punctuation are not perfect, so expect that I made some mistakes. I’m sure I did.
I hope this is helpful! ????