Which symbol should be used with numbers: a hyphen (-), or an en dash (–)? The question may seem trivial — a dash is a dash, right? — but using the correct symbol aids comprehension, just as commas and semicolons signal distinct grammatical structures, and no one will argue that those two punctuation marks can be used interchangeably.
Hyphens are used to separate groups of numbers, such as in telephone numbers or numbers of financial accounts. But for almost all other cases, the correct punctuation mark is an en dash, which indicates a range or a difference.
A span of years (such as “2009–2012”) or any other time range includes an en dash. (And note that “from 2009–2012” and “between 2009–2012” are incorrect; either use both from and to, or between and and, or neither.) The same treatment is given to a sequence of components, such as a range of chapter or page numbers or amounts (for example, “chapters 1–10” or “250–300 pages”).
A range of monetary amounts — and any other amounts — is also represented this way, as in “Salary range: $75,000–$80,000.” (Note that when expressing a range with very large numbers, to avoid confusion, the first number should not be abbreviated; for example, “$75–$80,000” means “from $75 to $80,000,” not “from $75,000 to $80,000.”)
Two contexts that cause confusion about which dash to use are scores and votes. These are not, technically, ranges, because nothing exists between them, as in the case of “2009–2012,” in which that time span includes 2010 and 2011 as well, and of “chapters 1–10,” which also includes every page between 1 and 10. But The Chicago Manual of Style, reasoning that the symbol between the numbers represents a difference between two values (and that the symbol is pronounced to), has elected to use en dashes for both types of representation.
Therefore, use an en dash to indicate scores for sports or other competitions (for example, “Her team won 6–3” or “They came back from behind to chalk up a 97–92 victory”). Note, however, that when a score does not immediately follow a verb or precede a noun, as in the examples above, it should be set off from the rest of the sentence by one or two commas: “East prevailed over West, 97–92”; “East prevailed over West, 97–92, for the league championship.” Win-loss records should also be formatted with an en dash: “The team went on to earn an 8–4 record.”
Votes are treated the same way: “The city council approved the project with a 5–2 vote.”
Many newspapers and websites follow the style recommended by the Associated Press Stylebook, which is to simply use a hyphen in place of an en dash. That preference presumably dates from the lead-type era, when compositors didn’t want to be bothered about trying to distinguish a – from a – on a piece of metal the size of a watermelon seed. Last time I noticed, however, producing an en dash was a simpler task. Dare to dash.