Capitalization

A. Just as you’d refer in Chicago style to a president of the United States or other country with a lowercase p (as in this sentence), you’d use a lowercase s when referring to a secretary of homeland security.

But note that the generic phrase “homeland security” (like “transportation,” “state,” and other such terms) becomes a proper noun when it refers to the administrative body—as in the Department of Homeland Security, or Homeland Security for short.

So you’d refer to the secretary of the US Department of Homeland Security. But this can get tricky: Does “homeland security” in “secretary of homeland security” refer to the department or only to the role? If in doubt, capitalize (“secretary of Homeland Security”). See also CMOS 8.22 and 8.63.

And before a name, secretary would be capitalized, as in US Homeland Security Secretary Alejandro Mayorkas, or Secretary Mayorkas.

A. In strict Chicago style, flight numbers would be lowercased—like room numbers, page numbers, and other such identifiers. Accordingly, we’d write “Pan Am flight 103” and, for subsequent mentions, “flight 103.” That’s the style Britannica follows in its article on the tragedy. According to this usage, “Pan Am” is a proper noun, whereas “flight 103” is not.

But you’re right that many sources capitalize flight numbers. If you’re going to go that route, however, you should still treat the airline name and flight number as separate terms, which would require a capital F even when the flight number is used alone: Pan Am Flight 103; Flight 103 (but the flight).

A. Words like “interstate” and “highway” are generally considered part of the name and capitalized: Interstate 90, Highway 66. But all the other terms in your list—from “aisle 8” to “terminal 1”—would be treated as generic and lowercased.

A. None of the terms you mention would normally be capitalized in direct address, even when standing in for a name:

Where are you taking me, driver?

Hey, bartender, where’s my drink?

But if the occupation can also be used as a title, capitalization is the norm:

How bad is it, Doctor?

What’s the rush, Captain?

Either convention can be broken, however.

For example, capitalization would make sense for a fictional character known by occupation alone, even if the occupation isn’t also a title—as in the case of the character known as “Driver” in the novels Drive and Driven, by James Sallis (Poisoned Pen Press, 2005 and 2012). And titles that aren’t being used literally are less likely to merit capitalization: What’s up, doc?

For some additional considerations, see CMOS 8.34–37.

A. According to Merriam-Webster, “sister” is “often capitalized” when referring to a member of a religious order, Catholic or otherwise. CMOS takes that “often” as permission to use lowercase: “The sisters left the convent at noon.”

A. We would, provided the randomness worked on some level. If a publisher has accepted the poem, then it probably does. A copyeditor might query any choice that doesn’t seem to be intentionally random—on the off chance that it might be a mistake—but otherwise, it’s usually up to The PoET.

A. If you’re in marketing, capitalize both of those words. Why be quiet about savings?

A. The noun bicentennial, like anniversary or birthday or even golden jubilee, is normally lowercased. But if you’re referring to a specific bicentennial, like the one the United States celebrated in 1976—“the Bicentennial”—a capital B might be warranted. Or so it seems in hindsight.

According to a Google Ngram comparison of the lowercase b and capital B forms of the word, there have been three notable jumps for “Bicentennial” in books published in English since 1900:

The two biggest bumps align with major bicentennials in the US (1976) and France (1989). The third peak—ca. 1932—corresponds to the bicentennial of George Washington’s birthday. (The ngram doesn’t tell you any of this—and there are other possibilities—but it’s fun to guess.)

In a publication that discusses one of the national bicentennials, a capital B would make sense. But note that both nouns and adjectives would qualify: the US Bicentennial, the Bicentennial celebrations in the US.

A. The advice in Chicago is supposed to highlight conventions that can be retained when importing bits of French into an English-language context, and capitalization is one of these conventions. But an initial article like le or la is most often changed to an English the, so to use your example, we’d refer to the Théâtre de la Porte Saint-Martin (starting the name with a capital T) even if, in a French context, it might be referred to as le théâtre de la Porte Saint-Martin (the theater’s website, however, capitalizes that first t).

To take another example, you might refer in English to the Bibliothèque nationale de France or, for short, the Bibliothèque nationale, both of which reflect French capitalization (which is evident in the abbreviation BnF, with a lowercase n). That would normally be Chicago style—that is, we’d retain the lowercase n in English. But it would arguably be clearer to refer to the Bibliothèque Nationale, with a capital N, so that readers unfamiliar with French capitalization would understand where the name begins and ends. Some editors depart from Chicago style for such terms (and apply English-style caps, a.k.a. headline style or title case) for this very reason.

Note, however, that for the title of a book or article or other work, which would normally be set off from the surrounding text by quotation marks or italics, French capitalization would always be retained (see CMOS 11.27). But for the name of a theater or a library or the like, you could make some exceptions for the sake of your readers.

A. The word “first” in “twenty-first” is an adjective, so it gets a capital F as the second part of a hyphenated compound in the name of an organization or the title of a work—or in a street name or whatever else would normally be capitalized. See CMOS 8.161, which also says specifically to capitalize the second element in a hyphenated spelled-out number. This advice was new to the 16th ed. (2010); until then, CMOS would have advised “Twenty-first,” but our editors agreed that the convention for lowercase wasn’t strong enough to continue to allow for an exception to the rule about adjectives. “Twenty-first” isn’t wrong, then, but it’s no longer Chicago style.