3.11: And / Or

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If you have ever read a lengthy legal document, you have probably encountered an abundant use of "and/or." Nevertheless, in good conscience, I cannot recommend that you use this construction in your writing, because the best style handbooks preach against it and label its use unprofessional. Besides, both "and" and "or" by themselves effectively link ideas that can be considered either individually or collectively. For example, in the second sentence of this paragraph, I used "and" to link "preach against it" and "label its use unprofessional," even though not every style handbook would necessarily do both of these. In other words, "and" can be used to suggest likely combinations of ideas, while "or" can be used to help the reader consider just one idea at a time.

If you feel, as some writers do, that you want to use "and/or" just to be fastidious, instead you should simply word the sentence appropriately to cover the different possibilities:

Instead of: "The new propeller design is expected to reduce cavitation and/or drag."

Write: "The new propeller design is expected to reduce cavitation, or drag, or both."