And/or, And, Or

 And/or
The construction and/or is criticised by grammarians, prose stylists and many legal drafters (both contractual and statutory). There are good reasons for this.

H.W. Fowler called and/or an ‘ugly device’. It looks as though you couldn’t take the time to think things through and express yourself other than by way of a fairly crude (if expedient) short form. And/or also has an air of the commercial purchase order to it.

There are other reasons to avoid and/or, and they relate to the meaning (and ambiguity) of words.

Disjunctive and, conjunctive or
We usually think of and as being conjunctive – that is, grouping things together – rather than disjunctive (separating things or presenting alternatives). Similarly, or is usually disjunctive. This is largely true, but not always.

Consider these examples:

The Minister of Finance may do X and Y [he can do both X and Y, but he is also free to do only one of them or neither – so and is not only conjunctive but also potentially disjunctive]

The Minister of Justice may do X or Y [here again, she could do either one or neither, but she could also do both – a conjunctive or is one possible interpretation]

To avoid confusion, you are better to say one of the following:

• both A and B
• A or B, but not both
• either A or B
• A or B, or both

Otherwise, your fate may be like that of the New Jersey judge in this recent case, where repeated use of and/or rendered her jury instructions so ‘hopelessly ambiguous’ that a new trial was ordered.

In contractual (and legislative) drafting, you probably want to avoid any ambiguity that might arise from and/or; in other kinds of legal writing, and/or just isn’t elegant.

Next tip: accentuating the negative

–Neil Guthrie (@guthrieneil)