Q. Recently the New York Times published an opinion piece by Mary Mann, a librarian and writer. In it she wrote, “In the past I’ve had to remind student patrons that you can’t cite Wikipedia on research papers.” Is that still the case?

A. Wikipedia, like any encyclopedia, is a tertiary source. A tertiary source synthesizes information in secondary sources to provide a summary for general readers about a topic. Secondary sources would include something like an article in a literary journal that analyzes the parallels between James Joyce’s Ulysses and Homer’s Odyssey. Ulysses and the Odyssey, in turn, are primary sources. Secondary and tertiary sources also usually refer to other secondary and tertiary sources in support of their own arguments.

So whenever you cite Wikipedia, you are citing a summary of mostly secondary (and some tertiary) sources on a topic. And for many readers, this thirdhand evidence won’t be enough to prove your point.

Summaries are incredibly useful, as the popularity of Wikipedia attests. They save us the trouble of doing our own research. For example, when something happens to a celebrity, or you need a historical overview of the Macintosh computer or a sense of the emerging consensus over climate change, start with Wikipedia. You can even tell your cousin what Wikipedia said about So-and-So’s untimely passing. But don’t write a paper that cites Wikipedia citing the New York Times and five other sources quoting the late actor’s rep saying it was due to “natural causes.” Your responsibility as a researcher is the same as Wikipedia’s: you must discover the facts for yourself—and prove them by citing them.

The good news is that you don’t have to credit Wikipedia if you use it to get leads on a subject. Wikipedia’s own source citations (and source citations in general) are a gift that anyone can follow.

Not that you can never cite Wikipedia. You can—for example, in a research paper that tracks gender bias in Wikipedia articles. But if you’re turning to Wikipedia in search of the truth, pay attention to the sources cited in its articles. Those, and not Wikipedia itself, are where the information comes from. Meanwhile, if you find something wrong in Wikipedia’s page on Sichuan peppers? Follow Mary Mann’s example and fix it yourself. Don’t forget to cite your sources.

Q. Should the names of houses be italicized as you would the name of a boat? What about if someone names their car?

A. A house, no. A car, maybe. For example, you wouldn’t use italics to refer to the White House or Graceland or Big Pink (the names of houses located respectively in Washington, DC; Memphis, TN; and West Saugerties, NY). But that last name, unlike the first two, is not all that well known, so quotation marks might be helpful for the first mention:

Several of the album’s songs were composed at “Big Pink,” the house in West Saugerties. . . . Before returning to Big Pink . . .

In general, however, the rule is simple: the names of houses, like other place-names, are capitalized but not italicized.

On the other hand, if you name your Subaru or Ford something other than Forester or F-150 (see CMOS 8.117), you could pretend it’s a boat and use italics à la Enterprise, a name shared by various military vessels and a series of fictional Star Trek spaceships (see CMOS 8.116). But those are official. Your pet name for your car is unlikely to merit such treatment except jokingly:

Cecil, my prized Celica, is in the shop.

Sorry to hear about Cecil. May he feel better soon.

Q. Should national anthems—for example, La Marseillaise—be set in quotes?

A. A national anthem is a song by any other name, but with more pomp and circumstance. So whether it’s “La Marseillaise” or “O Canada”—or “March of the Volunteers,” a song written in 1934 and later adapted as the anthem of the People’s Republic of China—put it in quotation marks.

Q. How do you show emphasis (and not with capital letters) in “thought” that’s already in italics?

A. If you must put thoughts in italics (italics are just one option among several), emphasis is usually shown by “reverse italics,” like this:

Does this mean no more waffles, like ever? That’s bad, very bad, I thought.

But you probably wouldn’t have written to us if regular type in an otherwise italic environment worked well as emphasis. Compare the same text but in reverse:

Does this mean no more waffles, like ever? That’s bad, very bad, I thought.

Readers are likely to miss the regular text in the first example (or to notice it but not understand it as emphatic); they are less likely to miss the italics in the second. But if you really want the words to stand out, try bold text or underscore (if your publisher allows it):

. . . That’s bad, very bad, I thought.

. . . That’s bad, very bad, I thought.

Underscore may be the better option. Thanks to the legacy of typewriters (and handwriting), it’s already understood as an alternative to italics. Bold, on the other hand, tends to jump off the page wherever it occurs, which could be either distracting or perfect, depending on the desired effect.

In sum, you have several options, among which is the option to use regular text for thought, reserving italics for emphasis.

Q. Is the example below correct? For the sake of consistency, I want to spell out the thousands (e.g., “470 thousand” instead of “470,000”), but I’ve never seen this done and don’t think it’s right. Is there a way to keep thousands and millions consistent within the same sentence? “We waste 470,000 heads of lettuce, 1.2 million tomatoes, 2.4 million potatoes, 750,000 loaves of bread, 1.2 million apples, 555,000 bananas, 1 million cups of milk, and 450,000 eggs every day.”

A. Consistency isn’t always a realistic goal with numbers. For example, no one would write a sentence like this one: “We counted 5.3 million fish in the year 2 thousand, but somehow I managed to catch only 3.4 tens.” In your example, “470 thousand” would be almost as intelligible as “470,000,” but the usual convention is to reserve a mix of words and numerals for millions and above—a cutoff designed to prevent strings of digits that are longer than their verbal counterparts would be (see CMOS 9.8).

Q. Hi! Hope you all are well. Please help me. I can’t find an answer anywhere. Does CMOS recommend “Gen Zers” or “Gen Zs”?

A. Merriam-Webster includes an entry for “Gen Z” as a noun. Under “Other Words from Gen Z,” the entry lists “Gen Zer or Gen-Zer” and “Gen Zers or Gen-Zers” (“or” means the hyphenated variants are equally common, but in such cases Chicago normally advises choosing the first-listed form). You won’t, however, find “Gen Zs”—which you can therefore assume occurs only as the plural form of “Gen Z,” as in more than one Generation Z (see CMOS 7.15 for styling the plurals of letters). For members of Generation Z, then, write “Gen Zers.” Ditto for their predecessors: “Gen Yers” and “Gen Xers.”

Q. Searching through CMOS, I can’t determine if this sentence is properly capitalized: “It is the sign that sat squarely on the Earth’s eastern horizon when you were born.” (It’s for an astrological publication.) Specifically, should the words earth, eastern, and horizon be capitalized, and is the “the” before Earth correct? Thank you.

A. Considered as a planet among other planets and bodies in our own solar system, “Earth” may be capitalized. In such contexts, “Sun” and “Moon” may also be capitalized, and “Earth” often appears without the definite article—like Mars and the other planets, but unlike the Sun and the Moon:

The Moon is much closer to Earth than the Sun is to Mercury.

If you (or your publication) prefer instead to write “the Earth” (as in your example)—and to use lowercase for the sun and the moon—that’s okay too. Just be consistent.

Questions like yours wouldn’t come up if not for the fact that there are many moons and suns besides our own, and the earth to us is both a planet and the substance on its surface (and the model for other earthlike planets). In ordinary prose—or in any generic reference that doesn’t depend on the identity of a specific astronomical body among other such objects, or where our own earth and sun and moon may be assumed—lowercase is almost always appropriate:

We learned that the moon is round, the earth is flat, and the sun is a golden orb.

Why on earth would anyone under the sun believe the moon is made of cheese?

Ganymede is Jupiter’s largest moon.

Circumbinary planets are planets that orbit two suns.

As for “eastern horizon,” that’s a relatively generic description, so lowercase is your best option. See CMOS 8.140 and 8.141 for a few additional considerations.