Q. Hi. Can you please outline your recommended approach to ordinals when using the alternative rule? Is it “seventh” and “17th”? And for centuries, using the alternative rule, do you recommend “17th century”? The general rule applies to cardinals and ordinals, but how about the alternative rule? Thank you for your time.

A. Chicago’s alternative rule for spelling out numbers, like the general rule, applies equally to cardinals and ordinals. If you’re following the general rule (and spelling out zero through one hundred), you would refer to the seventh and seventeenth centuries; for the alternative rule (zero through nine), you would refer to the seventh and 17th centuries. That approach works for occasional references to either or both centuries. But if you need to refer often to both one- and two-digit ordinals in the same context, you can use digits for all of them for the sake of local consistency (e.g., “the 7th and 17th centuries”). See also CMOS 9.7.