"Have some reason you" or "Have some reason why you"

Can the "why" be removed from the phrase "have some reason why you?"

Example:

Do you have some reason you ____?

vs.

Do you have some reason why you ____?

Are these both grammatically correct? What's the difference, if any? Googling I find a lot of both, but I'm still wondering about this.

Solution 1:

Well, since this issue's already come up once today, I guess I better elaborate my comment.

As it turns out, why may only be used in a relative clause that modifies the noun reason.
In much the same way, relatives with where must modify a place noun, and relatives with when must modify a time noun. While there are a lot of time and place nouns, there's only one reason noun, and it's reason.

Since the structure is so constrained, and so redundant, something is often deleted,
so that a simple tensed clause following reason implies why.

• He didn't tell me the reason why he wore a polka-dot dress.
• He didn't tell me the reason that he wore a polka-dot dress.
• He didn't tell me the reason he wore a polka-dot dress.

Similarly, leaving out the reason, but leaving in why, produces an embedded question clause
(also known as a free relative clause or a headless relative)

• He didn't tell me why he wore a polka-dot dress.

that also does the same job.

Solution 2:

Obviously the question is asking for a reason for what the person did, or is about to do. Without a "why", it wouldn't ask that question: "Do you have some reason you....(would like to tell?)" It doesn't ask the same question as "Do you have some reason why you did what you did?" Try it:

Do you have some reason you would like to do this?/ Sounds wrong for asking this question, and I believe is wrong.

Do you have some reason why you would like to do this?/Sounds correct for asking a question of this sort.

Basically, the first(without "why") is better for asking something like "Do you have some reason you would like to give/tell us?" It doesn't ask the person for the reason for doing something.

Solution 3:

I think this is quite a subtle issue. I agree with another answer that in OP's specific phrase, "why" is probably better. However, in this similar case...

• Is there some reason you don't want to come?
• Is there some reason why you don't want to come?

...I feel it's less important whether "why" is present or not. And insofar as I have an opinion at all, I would rather not include it.

This NGram has over 10,000 hits for "there some reason", of which it's obvious over half are questions that don't continue with "why". Plus 2670 for "there some reason why", which are nearly all questions.

In short, I think the distinction between "reason" and "reason why" largely comes down to individual style, and particular idiomatic usages.

Solution 4:

When spoken, both will work well. The why is something that follows naturally after reason, so it can be implied. When you say it, you already know what you want to say, so you don't need all the words that gives sentences structure.

When written, the second is easier to read. The why works as sort of a divider between the two parts of the question. Without the why you have to read the whole sentence before you can grasp its structure and figure out that there is an implied why in it.