Usage and Grammar

Q. I’m trying very hard to understand how through and to are different, as in “Monday to Friday” or “Monday through Friday.” Do they mean the same thing? To complicate matters, if an en dash is substituted (as in “Monday–Friday”), could the meaning be either through or to? I’m editing a paper that contains hundreds of date and number ranges. Sometimes the writer spells out to or through, but most of the time, he uses an en dash. I’ve read 6.78 a gazillion times and need further clarification. Thanks!

A. First of all, this is a clear case of an inclusive range— you are not dealing with scores or directions—so don’t worry about that different use of to discussed toward the end of CMOS 6.78. In this construction, to and through mean the same thing. (When after a gazillion attempts, you’re still stymied by something like this, sometimes it helps to step away from the style book and think a second about what you know. If a website said the library was open Monday through Friday, and if a newspaper ad said it was open Monday to Friday, and if the sign on the door said “Open Monday–Friday,” would you wonder whether they meant different things?) They need not, however, all be written the same way, except in places where it would look odd otherwise, such as in a single sentence, or in a list or table.