“And/or” — just plain dumb?

Over at Writing Matters, Leslie O’Flahavan cites five on-line style guides to support the proposition that “using ‘and/or’ in a sentence is just plain dumb.”

I wouldn’t go so far as to call it “plain dumb.” I do try to avoid it myself, because there are better ways to express the same idea. Logically, the disjunctive includes the conjunctive, so or has the same meaning as and/or. If you’re dealing with an illogical situation where or means one or the other, but not both, then write “A or B, but not both.” If you want to make it crystal clear that your situation conforms to normal logic, write “A or B, or both.” See Garner’s Modern American Usage 45 (Oxford 2003).