"If you or your colleague has" or "If you or your colleague have"?

Question

Which is correct out of the following two sentences?

1. If you or your colleague have any questions, let me know
2. If you or your colleague has any questions, let me know

I was originally thinking that #1 was correct because the sentence would be the following, if the colleague wasn't involved:

• If you have any questions, let me know

But then my mind was telling me that perhaps the "or your colleague" bit changes the subject or something, so the sentence could be written as follows, if you weren't involved:

• If your colleague has any questions, let me know

Answer 1

With a compound subject, the general rule is: If it uses "and", then clearly it's plural, so you should use a plural verb. If it uses "or", then the number of the verb should match the number of the LAST item in the list.

For example:

Either Bob or Fred has the answer.
Either Bob or the Thompson twins have the answer.
Either the Thompson twins or Bob has the answer.

(I haven't looked up a citation for this, but that's the rule I was taught in elementary school.)

Edit:

I see there is some disagreement, so I just did a quick search. Here's a link to a college grammar site: http://leo.stcloudstate.edu/grammar/subverag.html. They say:

If subjects are joined by or or nor, the verb should agree with the closer subject.

 

Either the actors or the director is at fault.

Subjects: actors, director; Verb: is

 

Either the director or the actors are at fault.

Subjects: director, actors; Verb: are

Answer 2

‘The Cambridge Guide to English Usage’ says that in such cases notional agreement suggests the plural verb, but that it’s ‘less than an elegant solution’ and advises redesigning the sentence. Doing so here would require something like ‘Let me know if you have any questions, or if your colleague has any.’ In practice I think this particular sentence would pass unnoticed with the plural verb.

Answer 3

For absolute grammatical pedantry, you could include both:

If you have, or your colleague has any questions ...

If you have any questions, or your colleague has, ...

However very few writers or speakers would go to those lengths.

If you or your colleague have any questions

... sounds most natural to me.

Answer 4

The speaker/writer is referring to a group of people collectively that includes you — you and your colleague — so should use the present tense, plural, second person form of the verb. In the case of to have that is have.

We don't tend to differentiate between plural and singular second person forms of verbs in English, so you can ignore that part really.

So

If you or your colleague have any questions

Is correct.

Similar to

If you or your family have any objections

You would use has if you were talking about something a third party was doing

If your colleague has any questions

Or

If your family has a dog

Because these statements exclude you (the second person) and the speaker/writer (the first person) and so only apply to the someone or thing not involved in the conversation (the third person).