Subscribe to The Chicago Manual of Style Online
Usage and Grammar
Q. Some guidance, please, on the use of (s) to indicate that a noun may be singular or plural, as in “The manager will interview the candidate(s).” I use the plural candidates to indicate there is at least one candidate but have been getting pushback from authors who ask for the source of my decision.
A. Although we aren’t crazy about the (s) solution, we do use it at times in CMOS. Another solution is to write “candidate or candidates,” but that’s a little clunky. Simply using the plural is often a good solution, but if it gives the wrong impression (e.g., that if there’s only one candidate, someone other than the manager will interview), then avoid it in favor of clarity.