Q. Hi. I have a question regarding the use of the em dash between two independent sentences (as in CMOS 6.91, last example). I understand that the dash can be used in place of a colon when introducing a list; however, when it is used to separate two independent sentences, as a semicolon would be used, it reads as a comma splice (as in your example): “The number of new cases has been declining—last week’s daily average was the lowest since January.” Wouldn’t a semicolon or period be better than an em dash in that example?
A. You’re right that a semicolon or a period might be better than a dash in that example. But we wanted our examples to show that a dash really can be used in place of just about any mark of punctuation. And don’t worry about creating a comma splice—only commas can do that.
It might help to show the same sentence but with parentheses:
The number of new cases has been declining (last week’s daily average was the lowest since January).
If you agree that those parentheses work, then consider that dashes and parentheses are usually interchangeable (though parentheses are not as abrupt as dashes, and they always come in pairs; see also CMOS 6.101).
But that doesn’t mean anything goes. Because dashes are so flexible, they tend to be overused. When in doubt, edit them out.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Is it acceptable to hyphenate an approximate measurement? Here are some examples: “I boxed up two-hundred-something widgets.” “It will take five-or-so days to complete.” “I need two-and-a-half months for a project of that scope.” (A half month is not a specific number of days.) Thank you for your help!
A. Hyphenation isn’t normally related to how exact a measurement might be. In your three examples, we’d apply no hyphens but one en dash (for the widgets):
I boxed up two hundred–something widgets.
It will take five or so days to complete.
I need two and a half months for a project of that scope.
According to Merriam-Webster, the word something in the sense you’ve used it—“some indeterminate amount more than a specified number”—is a combining form that connects to other words with a hyphen, as in “twenty-something years old.” When joined to the open compound “two hundred,” it gets an en dash in Chicago style (see CMOS 6.86). The other expressions of approximation in the examples above—“or so” and “and a half”—are ordinary phrases that don’t require hyphens.
[This answer relies on the 18th edition of CMOS (2024) unless otherwise noted.]
Q. Merriam-Webster lists “fact-check” as a verb (with a hyphen). But what about when it’s used as a noun—as in, “Oh no, not another fact check!” My guess is that it’s not hyphenated, but I would like to see an entry on this. Thank you.
A. We agree with your guess, so we turned to the OED for confirmation. That dictionary includes an entry for “fact-check” as a verb (with a hyphen) and another for “fact check” as a noun (no hyphen).
Interestingly, the noun and verb forms both first appeared in 1965, but in separate publications (according to the quotations in the OED entries). The verb appeared in a classified ad in the Chicago Tribune on February 7: “Loop encyclopedia needs science-oriented person to fact-check manuscripts”; the noun showed up in the University of Pennsylvania Law Review (vol. 113, no. 8, p. 1175): “Where more than a superficial fact check is required, the type of data typically provided in a presentence report is what might be desired.”
That job opening in the Loop sounds intriguing. If we had more time, we might do a fact check to find out which encyclopedia that was.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Should “cotton gin maker” have a hyphen? Does “cotton gin” here serve as an adjective, necessitating the hyphen? I’ve consulted CMOS and am still not quite sure. Thanks!
A. Good question! According to the hyphenation guide at CMOS 7.89 (see section 2, under “noun + noun, single function”), when a phrase like “cotton gin,” in which one noun (“cotton”) modifies another noun (“gin”), is used to modify a third noun (“cotton gin” modifies “maker”), the phrase would normally be hyphenated: cotton-gin maker.
That said, some editors would omit the hyphen. Not only is “cotton gin” entered as an unhyphenated noun in Merriam-Webster (with no adjective form, hyphenated or not, listed with it), but unless the surrounding context isn’t obviously relevant to cotton gins as opposed to some kind of process for making gin with cotton (whatever that would be), there isn’t much chance of confusion without the hyphen.
In sum, add the hyphen to be on the safe side, knowing that you can instead leave it out if that’s your strong preference (provided you’re consistent). In other words, this is a gray area (like the spelling of gray).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. I’ve been looking for a format on writing date ranges but cannot find any. How do I write a range without a death year or without a birth year? Should it be First I. Last (1804–?) or First I. Last (b. 1804)? Or is there any other way? What if you are unsure of the year because sources say different things?
A. If the person in question is no longer living, either form that you show is acceptable if all you know is a birth date: (1804–?) or (b. 1804). If the person is still living, you have the same two options (but without the question mark, and note the lack of a space between the en dash and closing parenthesis): (1984–) or (b. 1984).
If a death date but not a birth date is known, substitute a question mark for the birth date or use the abbreviation “d.”: (?–1890) or (d. 1890). To signal that a specific year of birth or death is likely but not definite, put a question mark after the year: (1804?–1890?). If the dates are contested, additional information may be provided in the text or in a note.
See also CMOS 6.68 and 6.79.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Do open compounds like “face mask,” “cell phone,” “sea level,” “high school,” and “life science” (all identified as nouns by Merriam-Webster) have to be hyphenated before a noun?
A. If a compound is listed as an open (unhyphenated) noun in Merriam-Webster, and the text seems clear without a hyphen, then you can leave the hyphen out even when the noun is used attributively (and even if the rules for hyphenation in CMOS 7.89 seem to suggest otherwise):
The face mask rules did not apply to cell phone users living in areas subject to sea level rise, regardless of the number of life science courses being taught to area high school students.
That seems clear enough without any hyphens. But if you do hyphenate any one of these compounds, you should hyphenate it everywhere else that it’s been used attributively. A consistency checker like PerfectIt can make this job a lot easier. See “Hyphenation in Context: The Chicago Manual of Style for PerfectIt,” at CMOS Shop Talk.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Hi! Is it ever appropriate to follow an em dash with a period if it’s the terminus of the sentence? Thanks!
A. You could try it, but there are probably better options. When an em dash marks a midsentence interruption of one speaker by another, as in quoted dialogue, it’s best not to use any additional punctuation (see CMOS 6.87):
“I thought I might—”
“Might what?”
A period after the dash would suggest that the sentence had come to an end rather than having been interrupted. But even if the speaker breaks off and then resumes speaking without a paragraph break, a period wouldn’t be necessary:
“I thought I might— Oh, it’s no use.”
not
“I thought I might—. Oh, it’s no use.”
Either option could work (and note the space after the dash in the first one), but the period in the second example makes the break seem less sudden.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. How would you handle “early-to-mid” + “century”? “Early to mid-twentieth century”? “Early-to-mid twentieth century”? “Early-to-mid-twentieth century”?
A. When these century phrases are used as nouns, we’d retain only the hyphen after mid: “in the early twentieth century,” “in the mid-twentieth century,” and, by extension, “in the early to mid-twentieth century.” But when they’re used as modifiers before another noun, extra hyphenation would be needed: “early twentieth-century history,” “mid-twentieth-century history,” and “early-to-mid-twentieth-century history.”
Two things to note: (1) It wouldn’t be wrong to refer to “early-twentieth-century history” (with two hyphens), but we think the extra hyphen (after early) is unnecessary (see CMOS 7.87—and note that early is an adjective, not an adverb, and therefore not subject to the -ly exception described in CMOS 7.86). (2) The word mid, unlike early, isn’t an ordinary adjective; instead, it usually combines with any word that it modifies—either with a hyphen (“mid-twentieth”) or without (“midyear”).
See also the hyphenation guide at CMOS 7.89, section 1, under “number + noun”; section 3, under “century”; and section 4, under “mid.”
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Working on an architecture book that uses a lot of duplex addresses—i.e., 1522-1524 Main Street. Thought it should be an en, but someone pointed out the numbers are not inclusive, as 1523 Main Street is not part of the address. Is that correct? Should it just be a hyphen? Thanks!
A. Whoever pointed out that the numbers are not inclusive has a very good point. A hyphen is the better choice than an en dash in that context.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Would it be correct to use an en dash instead of a hyphen in a compound like “singer-songwriter”? What about a slash?
A. En dashes may be used in compounds referring to two different people:
Epstein–Barr virus (a virus named for two people)
Ali–Frazier fight (a boxing match between two people)
a singer–songwriter duo (referring to two people)
but
Albers-Schönberg disease (a disease named for one person)
Though Chicago doesn’t require an en dash in those first three examples, some style guides do (notably in the sciences and in British English).
But when a compound refers to only one person or thing, as in the compound nouns singer-songwriter and city-state, most styles (including Chicago) would recommend using a hyphen.
As for a slash, that’s usually reserved for alternatives, where the slash means “or” rather than “and” (as in and/or but not singer/songwriter).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]