Usage and Grammar

Q. I write for an engineering training company. My boss returned from a standards meeting where the members decided that conditional sentences beginning with “when” (e.g., “When the diameter symbol is placed next to a dimension . . .”) are incorrect and should be changed to “where” throughout the standard and our textbooks. I contend that examples like these refer to “if or when” conditions, not place. It’s tantamount to saying, “Where you are in Paris, you must obey the rules.” Is there a rule that covers the correct usage of “where” versus “when”?

A. “When” and “where” have overlapping meanings; both can mean “in the situation of” or “in the event that” and are thus interchangeable in many contexts. (You can learn this in a dictionary.) Your engineers might need to follow rigid rules when they create building specs, but in writing, they would benefit from flexibility.