Q. You wouldn’t write “lineeditor,” so why “copyeditor”? Please help before my head explodes!
A. We know our preference for copyeditor isn’t popular with everyone, but judging from other copy words, it’s not all that weird. In American English, copy tends to form closed compounds, as this snippet from the 2003 first printing of Merriam-Webster’s Collegiate Dictionary (11th ed.) shows:*

With the sole exception of copy editor, each of those terms is closed up: copybook; copyboy; copycat, copycatted, copycatting; copydesk; copyedit; copyhold; copyholder; copyreader, copyread; copyright, copyrightable; copywriter. (Copyist is also one word, but it’s not a compound.)
One of them—copyrightable—even has the same number of syllables as copy editor, stressed in the same pattern.
Merriam-Webster has since added one-word copyeditor as a less common variant for the noun and two-word copy edit as a second-listed equal variant for the verb. Our preference splits the difference, favoring consistency with other copy words over the common usage reflected in the dictionary entry.
As for line editor, those two consecutive e’s preclude a move toward one word (à la linebacker or lineman), though we’d hyphenate the -ing and -ed participles as preceding modifiers, as in “line-edited manuscripts.”
We hope our answer has reached you in time.
* Note that those dots in the dictionary entries are called division markers. Not to be confused with actual hyphens, they show where hyphens may be added to words that need to be broken at the end of a line of text.
Q. Working on software that has an e-shop, I see a very different use of the word “checkout” vs. “check out.” Should it be “checkout now” or “check out now”?
A. A good dictionary will tell you that it’s “checkout” (one word) as a noun (often used attributively, as in “checkout line”) and “check out” (two words) as a verb. So it should be “check out now.” Or you could save yourself the editorial headaches and use “go to checkout” (or, as Amazon has it, “proceed to checkout”) rather than “check out now.”
Q. Does CMOS prefer “best seller” and “best-selling” per the dictionary spelling (over AP style of one word, no hyphen, for both)?
A. Because best seller (two words) is the first-listed spelling in Merriam-Webster (as of August 3, 2021),* Chicago would still recommend it, along with the hyphenated best-selling. But in 2017, when the seventeenth edition of CMOS was published, those—along with best-sellerdom and best-seller list (with hyphens)—were the only options listed in that dictionary. The spelling bestseller (one word) was introduced—as a second-listed equal variant—sometime after that.
As for AP’s preference for bestselling and bestseller, those are also relatively new, dating to May 2019. Meanwhile, the OED lists bestseller and most of its derivatives, including bestsellership and bestsellerism, as one word; the verb best-sell (with a hyphen) is the sole exception.
If this looks like a trend, it is—as a comparison of each iteration of “best seller” and “best-selling” in Google’s Ngram Viewer for books published since 1900 confirms (with a clear preference for bestseller and bestselling emerging in recent decades):

So unless you are obligated to choose the first-listed spellings in Merriam-Webster (e.g., for reasons of consistency in an ongoing project edited in Chicago style or to conform to house style), you’d be more than justified in preferring one word for bestseller and bestselling and the like. By the time the next edition of CMOS rolls around, we’d be surprised if these hadn’t become our first choices also.
[*Editor’s update: As of late 2022, Merriam-Webster has updated its entry and now lists one-word “bestseller” first, with two-word “best seller” as an equal variant.]
Q. I work at an arts organization that has two artistic directors. Should I refer to them as “co-artistic directors” or “artistic co-directors”?
A. Co–artistic directors. Otherwise they sound like directors who are artistic. (Chicago style would make that hyphen an en dash, by the way, but that may be too much to ask of an organization with two artistic directors.)
Q. I can’t find any consensus on this: does “quarter century” require a hyphen? Merriam-Webster doesn’t even have the term in its dictionary! (The nerve.) It seems that other online dictionaries do (and they also have a hyphen with “half-century”), but I thought it was odd that I couldn’t find “quarter century” referred to as a noun in either CMOS or M-W. Thanks!
A. Although “quarter century” doesn’t appear in CMOS, “quarter hour” turns up at 9.37 without a hyphen. When Merriam-Webster doesn’t include a phrase, you can assume that it doesn’t recognize it as a compound, and spelling it open is recommended.
Q. I recently read an article about a con artist who was described as “running a fine wine scam.” The ambiguity—is it a fine scam with wine or a scam with fine wine?—is driving me to drink. Is it acceptable in this situation to write finewine as one word to resolve the ambiguity? Please uncork me a good answer.
A. A hyphen will create the perfect pairing: a fine-wine scam. If in actuality it was a fine scam involving plonk, rewording will produce a less flabby finish.
Q. A colleague wants to use a hyphen in the phrase “Friday-afternoon lecture.” But isn’t this an overly rigid application of the phrasal adjective hyphenation rule in a case where it doesn’t apply? “Friday afternoon” is not a true phrasal adjective, but a temporal phrase. “Join me for Sunday morning brunch” is the same as saying, “Join me for brunch (on) Sunday morning.” Interested in your view on which is correct, and why.
A. “Noun + noun” phrases like “Friday morning,” where the first noun modifies the second noun, do qualify as phrasal adjectives. A hyphen increases readability, since Friday followed by a noun is not always part of a phrasal adjective: a Friday golf outing; a Friday birthday party. See section 2 of CMOS 7.89 (“noun + noun, single function”).
Q. Some compound adjectives are always hyphenated, even after the verb. Is worry-free hyphenated after the verb, as in this sentence: Audit trails and compliance tools make the process worry-free?
A. A compound formed with free as the second element is hyphenated both before and after the noun it refers to. (Whether such a phrase follows a verb is irrelevant.) Please see CMOS 7.89, section 3, under the word free:
toll-free number
accident-free driver
the number is toll-free
the driver is accident-free
Q. I see three different treatments for upper right in the Q&A responses: upper right, upper-right, upper right-hand. Are there any guidelines for this term? Is it hyphenated as an adjective and not as a noun? (“In the upper-right corner” vs. “In the upper right”?)
A. Yes: hyphenate the adjective and leave the noun open. Find guidelines for this kind of term and many others at CMOS 7.89.
Q. Is there a rule I can point to in self-defense to justify the following hyphenation of compound nouns: “in private- and business life”? Business life is an unhyphenated compound noun in this sentence, but the first term, private, is hyphenated by virtue of being separated from the second term of its compound form, life. Does that sound right?
A. Not quite. Private life and business life are simply two adjective-noun combinations (not compounds), which you compacted a bit in your example by not repeating life. Think of similar constructions that you probably wouldn’t even consider hyphenating; yours is no different:
in big and small matters
through textbook and online instruction
at public and private venues