Numbers

A. It is lucky that the ’20s, ’30s, ’40s, . . . , ’90s are so easy to talk about; it is unfortunate that the, um, zeros? ’00s? aren’t. In writing, “the ’00s” perhaps looks okay, but it reads horribly (the zeros? the aughts?); so, what does one say? I seem to recall that people writing about the first decade of the last century would say things like “in the first decade” or “at the dawn of the century” or “at the turn of the century” or something like that, phrases which lack economy and sometimes precision. Fewer writers speak of the “teens,” an expression that Chicago doesn’t favor. In any case, one can always use numerals: 2000–2009 or 2010–2019. That said, I wonder if and when something better will be dreamed up and successfully adopted.

A. It’s best to use the singular. For an example, see CMOS 9.21.

A. No commas should be used when numbers are written out:

103,000 = one hundred three thousand

The longer the number, the more awkward it may seem, but commas would make the number look like a series of smaller numbers, something that doesn’t happen with numerals because there are no spaces, for one thing.

A. Our rule is that all percentages and decimal fractions are set in numerals, in humanistic as well as scientific copy. The only exception is for the beginning of a sentence:

Zero percent of American-born participants in a recent poll could remember where they were—not to mention what they were doing—when Theodore Roosevelt was charging up San Juan Hill.

The ideal income tax, some people say, would be 0 percent of net income.

The sixteenth edition of CMOS makes this clear: Chicago’s general rule is to spell out zero through one hundred. See paragraph 9.2.

A. Chicago prefers the use of numerals for all numbers used as part of percentages, but use the word “percent” for humanistic copy and the “%” symbol for scientific and statistical copy:

humanistic:

10 percent (but spell out “10” if it begins the sentence)

scientific, statistical:

10%

A. See paragraph 9.5 in the sixteenth edition of The Chicago Manual of Style. Some writers prefer using and, but Chicago’s preference is to omit it.

A. In written text, Chicago’s rule is to write a cardinal rather than an ordinal, even though the number may be pronounced as an ordinal:

the events of September 11

the September 11 tragedy

September 11, 2001

When a day alone is mentioned, it is usually in the form of an ordinal but spelled out:

September 10, 2001, was the last day of its kind in the United States. The tenth will therefore always be important, even as it stands in the shadow cast by the eleventh.

As for an abbreviated form for September 11, “9/11” works fine (but see CMOS 16, paragraph 9.36).

A. Ah, yes, the infamous 8.3 of the fourteenth edition of CMOS. Earlier printings of the fourteenth edition applied sound logic. Look at the two-part rule: (1) the numbers one through ninety-nine are spelled out, and (2) the numbers one through ninety-nine followed by “hundred,” “thousand,” “hundred thousand,” “million,” and so on are also spelled out. It would be redundant to write in the first part that one through one hundred should be spelled out, because one hundred is covered by the second half of the rule (from which one can extrapolate that “one” followed by “hundred” should be spelled out).

Logical as this may have been, the wording confused many of us. So we changed the first part of the rule to make it clearer: spell out the numbers one through one hundred. The rule now confuses (almost) no one, even though it is a bit redundant.

In the fifteenth edition, we retained the clarity of later printings of the fourteenth. For the sixteenth, we’ve clarified that zero is also spelled out (see CMOS 16, paragraph 9.2).

A. We prefer hyphens or hyphens and parentheses, as follows (though you may choose to leave out “1-”—the country code for the United States and Canada):

1-212-555-1212 or (1-212) 555-1212

But unless you are constrained by, for example, an Internet form, it’s okay to use periods or slashes or even small bullets if you prefer. Any hyphens, parentheses, spaces, periods, etc. are aids to understanding the separate elements in a phone number. Where these aids are is more important than what they are; one does not, for example, dial (or more likely press) a parenthesis or a hyphen.

For international numbers, include the country code preceded by a plus (which indicates that additional numbers, depending on the origin of the call, are required). For example, a French number looks like this—

+33 1 00 00 00 00

—where “33” is the country code for France, “1” designates the Île-de-France region (which includes Paris), and the rest is the usual eight paired digits separated by spaces for French telephone numbers. From the United States, the plus sign signals the 011 needed to initiate an international call; from many other countries, it’s 00.

A. There is no general agreement about what a phrase like “turn of the nineteenth century” means. It does seem to suggest the “turn of the nineteenth century into the twentieth”—i.e., the change from 1900 to 1901 (or, popularly, 1899 to 1900). But it’s probably best to stick to the more general phrase “turn of the century” and to limit it to a context that makes the century in question clear—for example, in a discussion surrounding the immediate legacy of Theodore Roosevelt’s charge up San Juan Hill.