English

Normally I prefer "a large number of collisions are".

CJ had a good thread once about the difference between "A number of" and "The number of" but I can't find it.

A number of -- will take the plural. It means "many/most/several of the [whatever it is we're talking about]
The number of -- will take the singular. It refers to "the quantity."

Grammar GeekCJ had a good thread once about the difference between "A number of" and "The number of" but I can't find it.

A number of -- will take the plural. It means "many/most/several of the [whatever it is we're talking about]
The number of -- will take the singular. It refers to "the quantity."

However, there are differences of opinion about

Mr WordyHowever, there are differences of opinion about this;

What?!!! Impossible!

CalifJim A number of problems arise / *arises.

This definitely sounds bad, and (to me) worse than some other examples.

I think that people who use the singular verb probably make the choice on apparently logical grounds (to match "a number"), and in the belief that it must therefore be correct, but in violation of what feels most natural. It's a bit

"A large number of collisions is undesirable."

Is that cheating?

Mr Wordy"A large number of collisions is undesirable."

Is that cheating?

Because of "large", you mean? Or because the whole situation is undesirable when a large number of collisions are present?

CJ

CalifJimBecause of "large", you mean? Or because the whole situation is undesirable when a large number of collisions are present?

Something like the latter. It didn't seem exactly in the same spirit as the other examples.

Yes. Well, it just shows that misunderstandings can arise when the poster fails to provide at least one complete sentence as context.

CJ