Q. I edit documents in a corporate environment, and I have ongoing arguments with authors over the extensive use of and/or. I’m not convinced it should be used anywhere. What does CMOS think about it?
A. We use it occasionally but avoid it when possible. In the CMOS chapter on grammar and usage, Bryan Garner suggests that and/or “can often be replaced by and or or with no loss in meaning. Where it seems needed {take a sleeping pill and/or a warm drink}, try or . . . or both {take a sleeping pill or a warm drink or both}.”