The 18th edition of The Chicago Manual of Style (CMOS 18) provides guidance on when to use italics in professional writing. For US proposal writers and editors of government publications, applying these rules consistently helps keep documents clear, professional, and credible.
Italics are like fancy dress for words. Seeing a word in italics is like going into your local grocery store and seeing someone working there in a samurai costume. “Well,” you think, “you’re certainly here to tell me something.”
When to Use Italics in CMOS (18th Edition)
There are quite a lot of places we want to dress up words with italics. For some of us, there are too darn many places.
As The Chicago Manual of Style (CMOS 18, 7.51) admonishes us, “Overused, italics quickly lose their force.” But if we follow a manual like CMOS, it does say that we have to use italics in quite a few places.
Here’s an exhausting—but not entirely exhaustive—list of where to use (and not to use) italics.
1. For Emphasis
CMOS 18 recommends using italics for emphasis “only as an occasional adjunct to efficient sentence structure.” In other words, your sentences should make their point clearly without needing extra formatting to drive it home.
Some of us really like adding emphasis, but it’s a bit like laughing at your own jokes. You don’t need it if the words pack enough punch by themselves—which, generally, they should.
When writing US proposals and government publications, use italics sparingly. If every other word is emphasized, readers have a harder time figuring out which points really matter.
2. In place of underlining
In most ordinary text, italics serve the purpose that underlining once did. But when transcribing handwritten letters, you may want to preserve the writer’s original underlining, especially if they used double underlining or if you need to distinguish their emphasis from your own.
For example, the original letter might underline certain words, like:
“We wish you would come as soon as possible to retrieve your nasty little dog, which has destroyed all the rose bushes” [italics added].
Here, the underlining preserves the emphasis in the original letter, while the italics indicate emphasis added by the person transcribing it.
When editing a transcription for a government report or proposal, make sure readers can distinguish the original writer’s emphasis from any emphasis you add.
3. For Titles of Books, Magazines, and Albums
Titles of books, magazines, and albums are generally italicized. Shorter works, such as short stories, songs, and most poems, take quotation marks instead. Book-length poems are an exception.
Basically, if it’s a publication or work that stands on its own, it gets italics; if it’s a part of a larger work, it usually goes in quotation marks. A play or novel included in an anthology still takes italics.
And on the other hand, even if you’re holding in your hand the one-sided twelve-inch extended-play single of “I Was Made for Lovin’ You” by Kiss, it’s still not in italics, because it’s just one song, even if it does go on for almost eight minutes.
4. Not for the Periods or Commas Following Those Titles
The following punctuation is not part of the title, after all. This is where the eagle-eyed editors really get their bragging rights.
Don’t believe me? Just search “italicized period” on Twitter to find all the editors posting their wins.
This principle also applies when you're using italics for emphasis. Punctuation is italicized only when it belongs to the emphasized material. For example, the question mark in “Your mom is arriving tomorrow?” isn't part of the emphasized word, but the exclamation mark in “Yup!” belongs to the emphasized response.
When reviewing proposals, make sure periods, commas, and other punctuation marks aren't italicized simply because they follow italicized text.
5. Not for Words in Those Titles That Would Normally Be in Italics
Got that? Italics are like an on/off switch. If the title is already italicized, you generally switch off the italics for a word or phrase within it that would ordinarily be italicized. This is called reverse italics.
For example, Ursus arctos, the scientific name for the brown bear, would normally be italicized. But when it appears within an italicized book title, the formatting switches:
Winnie the Ursus arctos: A Child’s First Taxonomy Book
The same principle applies when a book title mentions another book. Instead of italicizing the title within the title, put it in quotation marks:
Fear and Loathing in Kant’s “Critique of Pure Reason”
6. For Abbreviations of Those Titles
The Chicago Manual of Style is, for short, CMOS, not CMOS. Enough said. Chicago style generally italicizes shortened forms of italicized titles, too.
However, the CMOS editors prefer CMOS without italics when referring specifically to their own manual.
If you're writing for an engineering audience, they suggest CMoS or simply Chicago to avoid confusion with the electronics acronym, which stands for complementary metal-oxide-semiconductor, a technology used in electronic circuits.
7. For Words Taken From Other Languages
CMOS 18 distinguishes between unfamiliar words from other languages and those that have become familiar in English.
Unfamiliar words and phrases are italicized, while familiar words generally appear in roman type. The choice depends on the context, how the word is used, and whether it appears in a standard English-language dictionary.
If a foreign word becomes familiar through repeated use throughout a work, it may need italics only on its first occurrence. Proper nouns generally remain in roman type, unless another rule applies, such as when they appear in titles of works.
The trick is deciding how familiar a word is. English has borrowed so much vocabulary from other languages that italics aren't always necessary. If you're unsure whether a word needs italics, it's often safer to leave it in roman type.
For more on this distinction, see the CMOS Shop Talk article on italics in context.
But Chicago style does italicize the Latin sic, as in “He said he was totally thicc [sic].”
8. For Words Qua Words
Sometimes, you're talking about a word itself rather than using it for its meaning. In these cases, the word is italicized.
For example, “Pulchritude is beauty, but the word pulchritude is rather ugly.”
The first use tells you what the word means. The second refers to the word itself, which is why it’s italicized.
9. For the Names of Ships
For example, “The USS Enterprise may have seemed to go where no one has gone before. However, the Ever Given tried the route never taken: a sharp right turn into the desert. It didn’t get far.”
The names of ships are italicized. If you mention a ship in a proposal or government publication, italicize its name.
10. For Certain Scientific Names
This includes genus and species names of living things, such as Cannabis sativa and Tyrannosaurus rex. In these two-part names, the genus is capitalized and the species name is lowercase. Both are italicized.
Other scientific terms follow different conventions. Gene symbols, enzyme names, and taxonomic ranks above genus and species aren't all treated the same way. For example, the family name Cannabaceae isn't italicized.
Sometimes, the common name of something is also its scientific name. We seem to do this especially with things that could kill us, like Boa constrictor and E. coli. In these cases, check your reference dictionary or the relevant scientific style guide. If the term is accepted as a lowercase common name, it may not need italics in that context.
11. In Various Ways in Legal Citations
This includes titles of articles and chapters, certain formal legal terms, and names of cases in running text—but not necessarily in legal citations themselves.
If you're preparing a US government publication or proposal that includes legal references, don't assume that CMOS alone governs the formatting. Follow the citation system required by the agency, client, or solicitation. For legal citations, that may mean consulting The Bluebook or another specified legal style guide.
If you're not working with legal citations, count your blessings.
12. For Certain Mathematical Constants and Variables
CMOS 18 recommends italicizing mathematical variables. For example, italicize p when reporting a study’s p value and n when referring to the number of subjects. In equations such as e = mc², mathematical variables are also italicized.
CMOS 18 no longer includes a separate mathematics chapter. For detailed guidance on formatting equations, consult a specialist mathematics style guide, such as the American Mathematical Society (AMS) Style Guide.
13. For Stage Directions
If you're editing plays, you probably know this. But if you're editing a book that happens to quote from, say, Shakespeare's The Winter's Tale, it helps to know how stage directions are presented.
For example:
”Well may I get aboard! This is the chase:
I am gone for ever.
Exit, pursued by a bear”
Stage directions are usually italicized in plays, but formatting varies by publisher. When quoting a play in a professional document, follow the formatting in your source.
14. For Rhyme Schemes
CMOS 18 (7.72) singles these out rhyme schemes for special mention. A rhyme scheme describes the pattern of rhymes at the ends of a poem’s lines. When you write the pattern using letters, italicize them.
For instance, abab indicates that the first and third lines rhyme, as do the second and fourth. The example below illustrates this pattern, with prickly rhyming with stickly and phallic rhyming with italic.
”Roses are prickly,
Anthuriums are phallic;
Chicago is stickly
On matters italic.”
An Easier Way to Check Italics
The list of rules and exceptions is daunting, and that’s just following one style manual.
What if you then have to consider house styles and industry conventions or individual client preferences? And then there are all the situations where you shouldn’t use italics, such as terms that require italics only on first use and not using italics at the end of the sentence? Even for those with the sharpest eyes and memories, it’s hard to avoid tripping up.
For proposal teams working under tight deadlines, these checks become more demanding when several contributors edit the same document. A final review needs to account for the applicable style guide as well as the organization's house style.
PerfectIt for MS Word has a wide range of consistency checks, including italicization. Its italics checks include:
Regular italics checks: A list of common terms from Latin, French, and German that may or may not be italicized, depending on your style guide.
The Chicago Manual of Style for PerfectIt: An additional check that covers hundreds of terms from Latin, French, German, Spanish, Hebrew, Japanese, and other languages likely to appear in English-language documents. It also includes many representative instances where italics are required.
PerfectIt can’t reasonably check everything that’s in italics; literally everything you could italicize could be the name of some work or vessel: an epic poem titled too darn many, for instance, or a sailboat named Yup! But it covers quite a lot, and it teaches you the principles and reminds you to look for other similar instances.
For US proposals and government publications, remember that CMOS is a reference point, not a substitute for agency-specific instructions, solicitation requirements, or your organization's house style. Check the relevant requirements first, then use PerfectIt to help maintain consistency throughout the document.
Are you using PerfectIt yet? If not, download the free trial. If you are, make sure you have The Chicago Manual of Style upgrade—it’s available for all PerfectIt users with a subscription to CMOS.
Frequently Asked Questions
1. When should you use italics in writing?
Use italics for specific purposes, such as emphasizing a word, formatting titles of standalone works, distinguishing unfamiliar foreign words, identifying words discussed as words, and formatting certain scientific names and mathematical variables. Under CMOS 18, italics should be used sparingly for emphasis so they retain their effect.
2. Do you italicize foreign words in English writing?
Not always. CMOS 18 generally uses italics for unfamiliar foreign words and phrases, while words that have become familiar in English usually appear in roman type. Context matters, and a word may need italics only on its first occurrence if it appears repeatedly. Check a current English-language dictionary and your applicable style guide when you're unsure.
3. How do you keep italics consistent in proposals and government publications?
PerfectIt helps you check and keep italics consistent in Microsoft Word through its regular checks and The Chicago Manual of Style for PerfectIt. You can also use custom instructions to apply your agency's or client's style guide alongside these checks, helping you keep formatting consistent across the document.