The top 10 things writers using CMOS should know

Mountains and lake at dawn

Every writer worth their salt works on their craft. Whether you’re reading competitors or doing grammar exercises, that writer brain of yours is learning. There’s a lot to learn, though, especially when you’re trying to match a specific style guide in your writing. Cheat sheet would be too generous of a name, but this article outlines the top 10 things you should know when using the Chicago Manual of Style.

Top 10 things writers should know in the Chicago Manual of Style

Chicago governs trade publishing quite firmly, though I can’t help but wonder how many people have read the whole thing. Don’t worry, I don’t volunteer you as tribute. It is a wonderful resource for spot-checking, however, and the online version has made it loads easier. If you’re not interested in your own copy, check out your local library for one you can use during your review. Or, keep this list handy to help with some of the usual suspects.

Remember, the following is not a fully inclusive list of how these elements are used. There are exceptions to almost every rule, but here are the 10 most useful things for writers using CMOS17 to know:

Em dash and ellipses

These trusty characters ( — and . . . ) are used to denote abrupt shifts in text or trailing thoughts. Both can also be used to introduce lists, and em dashes can stand in place of dialogue tags in some situations. Em dashes are also used in lieu of parentheses for parenthetical information—shocking, I know. An ellipsis can be used to elide (omit) content when quoting so you only repeat the really pertinent stuff. The ellipsis is the “blah, blah, blah” of the punctuation world when used like that.

Some examples:

  • My dog is really nice—most of the time.
  • Recently, we’ve seen an uptick in sales—before 10 a.m.—in all stores.
  • Maybe it would be different next year . . . then again, maybe not.
  • . . . really?
  • Consider the following . . .
  • On a fateful night, long ago . . .

Dialogue uses em dashes and ellipses quite regularly. The rules are the same there, but the spacing should be adjusted. I will deal more thoroughly with that below.

Notice that CMOS uses a closed em dash (no spaces around it) and spaced ellipses. This does not mean it can’t be your preferred style to use an open em dash or closed ellipsis—just add the rule to your style sheet.

In Britain, you’d used a spaced en dash instead of an em dash. That would look like this: Words and nonsense – more words and nonsense.

En dash versus hyphen

The en dash (–) serves a different function from the em dash, and even from the hyphen (-). CMOS has a really nice rundown on dashes in their FAQ, but it’s also unlikely the average bear is going to notice if you used a hyphen or an en dash. But I will. And so will other professional writers and editors, so might as well put this feather in your cap too.

An en dash represents a range of things. Whether that range is numerical, such as a range of dates like 1912–1914, or a range of words (an open compound phrase), like the Grey–Sloan Method, the en dash is there to show there’s a connection. Most readers don’t notice an en dash is bigger than a hyphen, but now that you do, you can’t unsee it.

Similarly, a hyphen connects two things to form a compound. Prefixes, suffixes, and all sorts of mishmash words use hyphens to indicate they belong together.

How do you know when to use a hyphen? Check your dictionary. I’m not kidding. Rules change on this all the time as usage overrides convention (and therefore becomes convention).

So you can have words like re-entry or reentry depending on the style guide you use, the dictionary it follows, and your own exceptions. CMOS17, in it’s section 7.89 hyphenation guide, says, “Chicago prefers a spare hyphenation style: if no suitable example or analogy can be found either in this section (7.81–89) or in the dictionary, hyphens should be added only if doing so will prevent a misreading or otherwise significantly aid comprehension.”

You should be using hyphens when creating linked adjectives like 17-year-old (seventeen-year-old, if you follow the numbers rule) or blue-green except in chemistry where compounds remain open. Remember adjectives come before a noun, so if you were to write either of these after the noun they describe, you would lose the hyphens.

Being ‘well-read’ can help you get a feeling for when to hyphenate from time to time, but you’ll be looking words up back-to-back to figure out when a hyphen is supposed to be used more often than not.

Punctuating dialogue

Dialogue is a lot easier to punctuate than you think. From the classic “she said” introduction to something more diabolical like introducing em dashes between speech fragments, dialogue needs to use punctuation that makes its intention clear.

Plain sentence structures can look like the following:

  • Jane said, “Yep, sure do remember how to do this from English class.” / “Yep, sure do remember how to do this from English class,” Jane said.
  • “And yet . . . ,” Toby replied. / Toby replied, “And yet . . .”
  • “I called for help, bu—” they started saying as the ground crumbled beneath them.

But what if you mix your punctuation?

  • Jane said, “Yep, sure do remember how to do this from English class,”—honestly, it’s basic!—”but I guess I can give it another look now.”
  • Toby looked up from what he was reading. “I know how you’re feeling . . . but it’s not going to help if you get angry!” He didn’t have time for this. “. . . Look, I know you’re trying to help. Just sit for a minute and let’s figure it out—okay?”

Your punctuation just has to match up. If you end a sentence or a thought, it needs to be reflected in the text. If your thought is more complex, mix your punctuation! Em dashes are excellent for helping you break a thought, but so are exclamation points, colons, semi-colons, etc. Make your punctuation work for you! Keep in mind, however, that the more complicated a sentence reads, the more work a reader’s brain has to do to understand it. Give readers a break by mixing things up.

Internal dialogue

Essentially, this is treated the same as regular dialogue. The difference between the two is that you don’t necessarily have to use dialogue tags to indicate you’re speaking internally. Oftentimes writers will use italics instead. If you’re already using italics in your dialogue (say for a second language), you might consider using single quotes instead of double or employing the em dash trick.

Some examples:

  • If she thought for one second that I wasn’t going to respond to this, that was her own fault.
  • Everyone began sitting down. It was obvious they had assigned seats, but . . . ‘Why then wasn’t I given my assigned seat? Great, now I have to stand here like a clown . . .’
  • —Oh, I definitely get it. You all suck.

If you set up internal dialogue well, you don’t need much to indicate that it’s happening. It’s important that you offset it if the dialogue is happening without the speaker being named, though, or find another way to address the situation that makes what’s going on clear to the reader.

Numbers and common symbols

Fun! CMOS is pretty adamant that you spell numbers out all the way up to 100. I’m pretty against that rule in casual writing, though there is a solid argument for it in fiction (especially fantasy). Fifteen hundred reads better than 1,500 in those types of texts, unless referring to a year.

This brings us to the official ruling by CMOS. They flat-out admit most fiction writers don’t follow the “write out numbers from zero to ninety-nine” rule. Instead, they suggest an alternate of writing out zero through nine, and start using numerals after 10.

The importance, as you may have noticed by now, is consistency.

The imitable Carol Saller wrote an article for CMOS called “Numbers in Creative Writing” which you can scope out here for several specific examples.

When it comes to symbols, do you write them out or use them? For example, do you use per cent, percent, or %? What about copyright © and trademark ™? These symbols, if you’re using them, need to be stylized correctly. Most word processors have them, but if not, you can find workarounds online. For CMOS users writing in fiction, use the words—and it’s percent, just so you know—to avoid any awkward reading. If it’s informal or the symbol is important, use it.

Remember that some symbols are easier to typecast then others when it comes time to publish. If you’re using symbols as a code in your book, make a note for yourself on secondary symbols you’d consent to use if what you want would be unclear in print. Your designer or publisher can help you with that call.

Title caps

Known as ‘headline style’, title capitalization follows some pretty basic conventions. There is some flexibility here, but consistency is key.

  • Articles the, a, and an are lowercase unless they’re the first word.
  • Capitalize the first and last word in titles and subtitles (unless it’s a species name, in which case it’s lowercase no matter what).
  • All major words like nouns, verbs, adjectives, pronouns, and adverbs get capitalized, and even some conjunctions (but never the common coordinating ones of and, but, for, or, and (the less-common common one) nor. Always lowercase as, and to gets lowercased when it’s a preposition and part of an infinitive.
  • Lowercase prepositions, unless they’re acting as adverbs or adjectives or are part of a Latin expression. For example, up in Turn Up or De Facto.
  • If a proper name is lowercased in text, it remains lowercased in a title.
  • Italicize foreign words.
  • Capitalize the first part of a hyphen. For the most part, capitalize the second part of a hyphenation as well (including numbers). Times you would lowercase include: When it’s a modifier following a music symbol; an article, preposition, or coordinating conjunction; and when it’s following a prefix that can’t stand by itself (like post or anti), unless it’s a proper noun or proper adjective.


How do you do citations, according to CMOS17? If you’ve had to do sourcing in school (citations, bibliographies, etc.), this will be pretty familiar romping ground for you. Moving on from academics, the rules look something like this:

  • Italicize books and periodicals, movies and films, TV and online streaming shows, podcast programs and series, radio shows, and video games.
  • Use quotation marks for articles, chapters within larger works, and other shorter literary works, as well as for single episodes of TV, radio, or podcast shows.
  • The names of the networks, channels, streaming and hosting services, etc. are in plain font (roman).
  • Websites should be done in title case, with ‘the’ lowercased unless it starts a sentence. Page or tab names, sections, or other identifiers like special features get treated with quotation marks, but no italics. Do include shortened website URLs where possible.

Not-so-serial comma

The serial or Oxford comma aims to add clarity to a sentence. Listed items and compounds of more than two have a comma separating each. Do you prefer the less-is-more approach to writing? Add the exception to your style sheet.

There are times when no number of commas is going to save you. And, really, if you find yourself making a complicated sentence (without cause), maybe you should consider recasting anyway. Complicated doesn’t necessarily mean long, by the way. Sometimes a third comma can make it sound like you’re making an appositive (a secondary explanation) instead of list.

For example: We went to a restaurant, Dasher’s Point, and a movie.

In this example, is Dasher’s Point a restaurant or a destination? A simpler way to write it is using three ands—We went to a restaurant and Dasher’s Point and a movie—or to rework it for something more prosaic.

S, es, s’s, ss?

How do you form a possessive from a word that ends in -s? What if it’s plural? Do you just add an s?

This YouTube video clip of comedian Brian Regan’s standup routine, “Stupid in School,” always puts me in stitches. The English language is a beautiful travesty. #MOOSEN

So… you don’t always just put an ‘s’ on it? Right. Here are some good-to-remember plural and possessive rules:

  • Check your dictionary.
  • If you have a plural word inside quotation marks, the s goes inside.
  • Do you have italicized foreign words? The plural addition should also be italicized.
  • You add a roman s to the italicized title. Your book title, if already plural, can be left alone otherwise.
  • Ifs and buts (not if’s and but’s); dos and dont’s (not do’s and don’t’s).
  • Most singular nouns are made possessive by adding an apostrophe s (dog’s ears), as are plural nouns that don’t end in -s (children’s clothing). And most plural nouns ending in -s are made plural by just an apostrophe (cats’ eyes).
  • Although you wouldn’t say it, proper nouns that make an ‘eez’ sound at the end take an apostrophe s (Pleiades’s).

Some of these might seem like awkward solutions, and they are. You can always rephrase! And you should.

Text-within-text (text messages, letters, etc.)

Now for a formatting note, with CMOS guidance. If you’re writing something where another medium is being used in the book and either quoted or reproduced for effect, it needs to be set off from the main text somehow. There are a few ways to do this without making your page look too busy, just be consistent.

  • Set off the text in a block quote, like you would with more traditional material.
  • Use italics (if not already deployed for internal dialogue or other purposes).
  • Instant messaging or texting can be shown as left- and right-justified text for the back-and-forth. You could also put the speaker’s name in brackets or similar to show who’s chatting.

When you get to the publishing stage, you can communicate what you’d like this type of material to look like to your designer or publisher. They’ll let you know what’s possible!

Published by M Gardner

Editor and writing coach. I'm keen on helping establish and grow unique authorial voices for maximum impact in the reading world.

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