Q. Do you hyphenate “student teacher”?
A. We follow Merriam-Webster and leave it open: “student teacher.” The term, in which “student” modifies “teacher,” is analogous to “student nurse,” which appears in section 2 of our hyphenation table (CMOS 7.89) under “noun + noun, single function (first noun modifies second noun).” Compare “writer-director,” in which the nouns represent two separate (and grammatically equal) functions.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Does the Manual defend “on a case-by-case basis” over “case by case”?
A. Yes—we would hyphenate. You can deduce this preference from CMOS 7.87: “Multiple hyphens are usually appropriate for such phrases as an over-the-counter drug or a winner-take-all contest.” Hyphens in such phrases aid readability by helping readers to differentiate a modifier of otherwise indeterminate length from the word or words that it modifies. Postscript: As to whether we would defend “on a case-by-case basis” as a phrase, it’s an established idiom and might be preferred in some instances to the more concise “case by case” on that basis alone (so to speak). (Compare “pets will be permitted on a case-by-case basis” to “pets will be permitted case by case.”) But if you’re considering a shipment of beer, you may need to examine it case by case (literally). It’s best to take a case-by-case approach.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. I know that the CMOS preference is not to hyphenate “noun + gerund” compounds, but in the case of “decision-making,” which appears with the hyphen in many dictionaries, would CMOS call for a hyphen? Thank you in advance!
A. Here’s what our hyphenation table says, under “noun + gerund”: “Noun form usually open; adjective form hyphenated before a noun. Some permanent compounds hyphenated or closed (see 7.82).”
If you follow the link to paragraph 7.82, you will see that a permanent compound is a compound that’s listed in the dictionary in any form—open, hyphenated, or closed. In Merriam-Webster, our dictionary of choice, the hyphenated compound noun “decision-making” appears as such, so it’s always hyphenated. (Most adjective forms, on the other hand, can be left open after a noun, even if they are listed in the dictionary with a hyphen.)
In CMOS 16 (published in 2010), “decision-making” was not yet listed in Merriam-Webster. But M-W added it in time for CMOS 17 (published in 2017). So whereas CMOS 16 shows the noun form “decision making” in its table, CMOS 17 has “decision-making.”
We hope this helps with your decision-making efforts! (As a preceding modifier, “decision-making” would be hyphenated even according to CMOS 16.)
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. When referring to year ranges, I have an author who insists on using “during 1940–45.” I’ve seen “from 1940 to 1945” and “between 1940 and 1945” and simply “1940–45,” but other prepositions sound awkward in this context. To me, something happens during an argument, the winter, the ’80s, an era. That is, something that has a beginning and an end but where those time points aren’t explicitly stated. I would love to hear your thoughts on the matter!
A. It’s like you say. The preposition “during” (like “in”) makes sense with a single event or period; it doesn’t quite work with a period expressed in terms of a beginning and an end. You can write “during the war,” but “during 1940 to 1945” is awkward. So change “during 1940–45” to “from 1940 to 1945” or “between 1940 and 1945”; the former emphasizes the whole range, the latter can be less specific. Or, as a last resort, add “the years”: “during the years 1940–45.” See CMOS 6.78 for more examples.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Is the hyphenation in the following sentence incorrect, or is it just not Chicago style? “He had only two seasons with twenty-or-more homers.” Thanks for another great year of Q&A!
A. The hyphens in “twenty-or-more homers” are contrary to Chicago style and also incorrect. The phrase “twenty or more” describes two separate quantities; hyphens would illogically suggest a single quantity of “twenty-or-more.” On the other hand, hyphens are helpful (and strictly Chicago style) in a phrase such as “two twenty-or-more-homer seasons”—though “two seasons with twenty or more homers” is easier to read.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. In your hyphenation table (CMOS 7.89), why is “mid-twentieth” in “mid-twentieth century” hyphenated? Shouldn’t it be closed up as “midtwentieth century” or have an en dash instead of a hyphen?
A. That’s a good question! The fourteenth edition (1993) did advise an en dash: “mid–twentieth century.” But we decided as of the fifteenth (2003) that this was just too fussy. The hyphenated form lends itself better to compound modifiers, as in “mid-twentieth-century furniture.” So when the less common noun phrase is used, we prefer to retain the hyphen: “mid-twentieth century.” A similar logic has discouraged us from advising “midtwentieth century”—though we do recommend “midcentury.”
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Do you recommend using en dashes and em dashes in tweets? Or hyphens?
A. There are no obvious reasons not to use en dashes and em dashes in tweets aside from the extra effort they require to enter properly. To get either of them from a virtual keyboard, try holding down the hyphen to see more options (including en and em dashes); on physical keyboards, you’ll need a keyboard shortcut (e.g., Alt+0150 and Alt+0151 using the numeric keypad in Windows or Option-Hyphen and Option-Shift-Hyphen on a Mac). Or you can copy and paste from a word processor. But don’t feel obligated. If you’re in a hurry—or if it’s just not your style—you can use a hyphen (-) where an en dash (–) might be best, or two hyphens (--) or a space-hyphen-space ( - ) instead of a true em dash (—).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. What is correct style: “X and Y axes” or “X- and Y-axes”?
A. In the context of the Cartesian coordinate system, the hyphens are conventional: “X-axis and Y-axis” or “X- and Y-axes.” But unless the axes have been specifically labeled with capital letters, they are usually referred to as the x- and y-axes. In nonmathematical contexts (e.g., to refer to a simple chart or graph), the hyphens are often omitted, as in “x and y axes,” which has the advantage of not requiring a suspended hyphen. Consider your context and be consistent. For suspended hyphens, see CMOS 7.88; for math, see chapter 12.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. What combination of hyphens or en dashes is used to punctuate “a four hundred year old shipwreck”?
A. Please, no en dashes! Write “a four-hundred-year-old shipwreck.” When it comes to compound modifiers, en dashes are useful mainly for expressions that include a compound term that’s always left open: “World War II–era shipwrecks.” In your example, there’s no reason “four hundred” can’t be hyphenated and joined to the rest of the modifying phrase by another hyphen; only rarely, if ever, should a compound contain a mix of hyphens and en dashes. See CMOS 6.80 for more details.
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]
Q. Hello, No hyphen after a number and before the word “percent”; that’s the rule, per Chicago. But if part of a longer modifier, would the following be correct? Mike said, “A 15-to-20-percent-a-year increase in sales is what’s expected.” Thank you.
A. That’s tricky, but it doesn’t need to be. Just change “a-year” to “yearly” or “annual” (and edit out the redundant “what’s” while you’re at it). Now you have “a 15 to 20 percent annual increase in sales is expected.” Or you could use an en dash in place of “to”: “a 15–20 percent annual increase . . .” (see our hyphenation guide, under “number + percent”).
[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]