It's best to avoid using and/or, but what should you do if you have to use it?

Mignon Fogarty,
September 16, 2015
Episode #481


Kelly asked whether and/or in a subject makes the verb singular or plural. For example, what verb should she use in a sentence like this:

This message and/or attachments [is? are?] confidential.

You'd be hard pressed to find a style guide that doesn't admonish you to drop and/or and rewrite the sentence with just and or just or.

If you feel you must use and/or, my nonscientific survey of professional writing shows that you probably want to treat and/or as though it makes the subject plural. For example, Kelly's sentence would read

This message and/or attachments are confidential.

Usually, rewriting the sentence with or better reflects the meaning you're trying to accomplish with and/or, but sometimes people try to add clarity by adding or both to the end of the sentence:

This message, or attachments, or both are confidential.

In Kelly's case, a slight rewrite with and is probably the best choice:

This message and any attached files are confidential.

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