Introducing The Chicago Manual of Style for PerfectIt

Editors are trained not only to look for errors but also to account for contextual nuances and stylistic preferences. We impose consistency and clarify ambiguous prose, and we know when and where to look things up. To make sure we haven’t missed anything, we make use of spelling and grammar checkers.

Some of us also take advantage of word-processing macros and add-ins to help us clean up and format our documents and to zero in on hard-to-find errors. One such tool is PerfectIt, a proofreading add-in for Microsoft Word that looks for inconsistencies and other problems that Word tends to miss.

And now there’s a brand-new option: The Chicago Manual of Style for PerfectIt includes built-in advice from CMOS and a range of checks that are designed to support Chicago style.

If you already have a PerfectIt subscription and a subscription to CMOS Online, you can start using Chicago Style for PerfectIt right away (at no additional cost). Here’s how. If you need a subscription to either one, find out more here.

To learn more about how Chicago Style for PerfectIt works, keep reading.

What PerfectIt Does

PerfectIt’s primary function is to scan Word documents for inconsistencies.

For example, say your document includes offline in some locations and off-line in others. Both versions are “correct”; dictionaries vary, and Word won’t flag either one. When PerfectIt finds both, it will list all occurrences and give you a chance to review them in context. You can then fix the ones that don’t match your preference.

In addition to hyphens, PerfectIt checks for inconsistencies related to spelling, capitalization, abbreviations, italics, numbers, and lists, and it will look for quotation marks and parentheses or brackets that have been left open, among other checks.

PerfectIt also includes a number of built-in settings that can be adjusted to enforce specific preferences. For example, you can set PerfectIt to prefer FBI to F.B.I. and 1990s to 1990’s and to look for spelled-out numbers above a specified range. You can also add your own spelling preferences.

Any of PerfectIt’s built-in style sheets can be customized (including the new one for Chicago style), and you can create your own style sheets from scratch.

How Chicago Style Enhances PerfectIt

Chicago Style for PerfectIt does more than simply check for inconsistencies. It will also stop on words and phrases that are not in Chicago style and suggest the preferred forms. And because it gives you advice directly from CMOS, you won’t have to leave the program to look up the rule.

For example, do you know whether Chicago prefers “Asian American” (no hyphen) or “Asian-American” (hyphen)? Does it matter whether it’s a noun or an adjective? Would it be “a de facto government” (with italics for the Latin term) or “a de facto government” (no italics)? Should “de facto” be hyphenated because it precedes the noun it modifies? Does Chicago prefer “10 AM” or “10 a.m.” (or “10am”)? What’s the plural of “court-martial”? How do you form the possessive of “virus” or “Dickens”? Is it “Covid-19” or “COVID-19”?

To see how this works, let’s run through some examples, starting with those.


If Chicago Style for PerfectIt finds the term “Asian-American,” with a hyphen, it will suggest “Asian American” and list each occurrence of the hyphenated version in the document:

Screenshot from Chicago Style for PerfectIt. Hyphenation of Phrases. The term “Asian American” is usually open in both noun and adjective forms. See more from CMOS 7.89. Preferred style: Asian American. Asian-American [found 1 time] …to Asian-American individuals and communit… Fix

Clicking “Fix” on any one of them will replace the hyphen with a space. Chicago leaves terms like “Asian American” open in both noun and adjective forms, as an excerpt from CMOS 7.89 explains:

Screenshot from Chicago Style for PerfectIt. The Chicago Manual of Style. 7.89, proper nouns and adjectives relating to geography or nationality. Compound terms relating to geography or nationality are usually left open in both noun and adjective forms, unless the first term is a prefix or unless between is implied (e.g., “African Americans”; “African American president”; “a Chinese American”; but “Sino-Tibetan languages”; “the Franco-Prussian War”; “the US-Canada border”; “Anglo-Americans”). See also 8.39. …to Asian-American individuals and communit… Fix

If you need more info from CMOS, the red paragraph numbers link directly to CMOS Online.


According to CMOS 7.54, Chicago prefers regular text for a familiar Latin word or phrase like de facto unless it’s referred to as a word or phrase (as in this sentence) or emphasized in some way (see also CMOS 7.50 and 7.63). And according to CMOS 7.89 (section 1, under “non-English phrases”), Chicago doesn’t add hyphens to phrases borrowed from other languages, even as adjectives before a noun. So Chicago Style for PerfectIt will stop on “a de-facto government” twice—first to suggest getting rid of the hyphen and then again to suggest using regular text instead of italics.

Time (“a.m.” and “p.m.”)

According to CMOS 10.41, Chicago prefers “a.m.” and “p.m.”—lowercase and with periods—when referring to time of day (as in “10 a.m.”). So Chicago Style for PerfectIt will look for a numeral followed by either “AM” or “PM” or “A.M.” or “P.M.” (in full caps or small caps) or “am” or “pm”—in each case, with or without a space between the numeral and the abbreviation. It will also look for “one AM” or “one A.M.” and “two AM” or “two A.M.” and suggest “one a.m.” and “two a.m.” (and so on).

If, on the other hand, your document has “12 a.m.” or “12 p.m.” (or a variant thereof), PerfectIt will suggest using “midnight” or “noon” instead, in line with CMOS 9.38.

As with any PerfectIt check, you get the chance to review each item and decide what to fix on a case-by-case basis, and you’ll get an excerpt from CMOS if you need it.


If PerfectIt finds the spelling court-martials, it will suggest using the plural form courts-martial instead—but with a reminder that court-martials may be correct as a verb. PerfectIt will also look for variants of the term with a double el (e.g., court-martialled) or without a hyphen (or both). Chicago defers to Merriam-Webster for most spellings, including plural forms, but in this case the usage glossary at CMOS 5.250 includes an entry on court-martial, which PerfectIt will display as needed when it flags an incorrect variant:

Screenshot from Chicago Style for PerfectIt. The Chicago Manual of Style. 5.250, court-martial. Two words joined by a hyphen, whether the phrase functions as a noun or as a verb. Because martial acts as an adjective meaning “military,” the plural of the noun is courts-martial. The third-person-singular verb is court-martials (e.g., “if the general court-martials him, he’ll have much to answer for”). In American English, the inflected spellings of the verb are court-martialed, court-martialing; in British English, the spellings are court-martialled, court-martialling.


Chicago adds an apostrophe and an s to form the possessive of a singular noun, including singular nouns ending in s (see CMOS 7.16). So when PerfectIt finds virus’, it will suggest virus’s. Singular forms of proper nouns are treated in the same way (CMOS 7.17), so if your text includes a phrase like “Dickens’ manuscript,” PerfectIt will suggest “Dickens’s manuscript.”


Some sources prefer “Covid-19” (capital C only), treating other acronyms similarly; some even prefer “covid-19” (all lowercase). But Chicago prefers all-caps “COVID-19” (see CMOS 10.6 and this post on CMOS Shop Talk), so Chicago Style for PerfectIt will stop on variations that aren’t in all caps.


According to CMOS 9.18, percentages are expressed in Chicago style with the word percent. So when PerfectIt finds a number followed by the symbol %, it will suggest changing it:

Screenshot from Chicago Style for PerfectIt. Style Points. Unless the context is technical or scientific, express percentages using the word “percent” (e.g., “3 percent,” not “3%”). Preferred style: percent …of cases increased 27% in the first year… Fix

An excerpt from CMOS explains the rule:

Screenshot from Chicago Style for PerfectIt. The Chicago Manual of Style. 9.18 Except at the beginning of a sentence, percentages are usually expressed in numerals. In nontechnical contexts, the word percent is generally used (e.g., “3 percent”); in scientific and statistical copy, the symbol % is more common (e.g., “20%” [with no space between the numeral and the symbol]). Note that in an expression involving more than one quantity (as in a range), the symbol is repeated but not the word percent (e.g., “a 20%–25% increase”; but “90–95 percent”). See also 9.17. …of cases increased 27% in the first year… Fix

A separate check will look for a spelled-out number followed by percent and suggest using a numeral instead.


By default, Chicago Style for PerfectIt looks for numbers up to one hundred expressed as digits and suggests spelling them out according to Chicago’s general rule (CMOS 9.2). But it will ignore expressions where digits are usually correct (like “3 percent” and “page 5”). And it can be adjusted to support Chicago’s alternative rule of spelling out numbers up to nine (CMOS 9.3).

PerfectIt will also look for periods and commas next to quotation marks, hyphens in simple fractions like one-third, and a few other styles for which Chicago has a definite preference.

What Chicago Style for PerfectIt Won’t Do

Chicago Style for PerfectIt will flag a long list of things that don’t match Chicago’s preferences. But it won’t find everything, and it won’t automatically apply Chicago style to your documents. Instead, it is designed to teach the principles of Chicago style as you run PerfectIt and review your text.

For example, PerfectIt might stop on the word resume (no accents) or resumé (one accent) and suggest résumé (two accents) for the sense of curriculum vitae or summary. But to avoid stopping on every instance of the verb resume, PerfectIt looks for only a few phrases where the noun résumé is likely to be correct. It’s up to you to learn this preference and to apply it elsewhere as needed.

Many of PerfectIt’s suggestions are less complicated than that. For example, the spelling ginkgo would be preferred over the less common variant gingko in almost any context. But false positives—which happen whenever a usage that’s correct gets flagged as a potential error—are inherent in any spelling or grammar checker, and PerfectIt is no different.

For example, Chicago Style for PerfectIt would flag the variant spelling for ginkgo in the previous paragraph as an error even though it’s used intentionally. Or, to cite a more general example, if you refer to “thirty five-dollar bills,” a grammar checker may be fooled into suggesting a hyphen between thirty and five—whereas there is no such thing as a thirty-five-dollar bill.

If anything, PerfectIt will turn up more false positives than Word does, because many of PerfectIt’s checks are for terms that are correct according to some styles but not others, or that would be correct in one context but not another. In other words, PerfectIt is looking specifically for problems that require editorial judgment and expertise to resolve.

Finally, PerfectIt doesn’t currently check source citations for Chicago style. While PerfectIt plans to add citation-checking capabilities in time, the focus for now is on the rules and recommendations in CMOS that apply to all writers and editors.

Learn More

Chicago Style for PerfectIt won’t apply Chicago style for you, but it will save you the time it normally takes to find a rule in CMOS. This makes PerfectIt a good tool for keeping up with the details of Chicago style with minimal effort. And it comes with all the benefits of PerfectIt’s consistency checks and custom style sheets, giving you an edge when it comes to tracking down errors that editors and Word both tend to miss.

To learn more about The Chicago Manual of Style for PerfectIt or to apply it on your next document, click for details.

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