Is the following sentence grammatically correct?

Do you know why this works this way?

It looked a bit suspicious to me, so I googled it — to find only four results. If the sentence above is incorrect, would you suggest alternatives? Maybe, "Do you know why does this work this way?"

closed as off-topic by Kris, Ellie Kesselman, Chenmunka, user66974, ermanen Oct 26 '14 at 23:26

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  • 1
    Your alternative is clearly ungrammatical, and of course Google is not an indicator of grammaticality. Most grammatical sentences have not been produced yet, much less posted on the Internet, much less indexed by a search engine, much less indexed by Google. – RegDwigнt Oct 24 '14 at 20:22
  • Thank you. I know Google is not the most trustworthy source of grammaticality. I would argue that from the total number of sentences produced in the internet, it is more likely to find grammatical sentences than ungrammatical ones. Do you know an alternative source of information for this type of question? – Robert Smith Oct 24 '14 at 20:31
  • @RegDwigнt Can you elaborate why the alternative I proposed is ungrammatical? Are you suggesting that the original sentence is okay? – Robert Smith Oct 24 '14 at 20:39
  • 1
    Yes, the original is okay, and yes, the alternative is ungrammatical and we have quite a few questions on that. A quick search found this one, but I know there are better candidates and I shall post them should I find them. In the mean time, you can follow the trail of "related questions" from that one by yourself, or check the inversion tag. – RegDwigнt Oct 24 '14 at 20:45

"Why this works this way" is a dependent noun clause. "Why does this work this way?" is an interrogative sentence. You're not asking why thing works. You're asking a different question "Do you know" about the fact "why this works". Interrogative sentences are inverted, which explains the word order difference. The noun clause is not inverted, since it's not interrogative.

Change the words up for something simpler, and it will be obvious:

"Do you know why the wood burns"? "I know what he likes".

The awkwardness you're perceiving in the original has more to do with the repeated "this" than the clause structure.


While I can't think of a specific grammatical rule that is being violated, the sentence does suffer from an ambiguous clause. In common usage, "this" is used as the subject of a clause when spoken aloud, and is commonly followed by a clarification question. For example- "Did you move this?" "Move what?" Since the reader cannot ask for clarification, the sentence should either be written "Do you know why it works this way?" or "Do you know why (Name the object in question) works this way?" This gives the reader context. For me it is a stylistic and clarity issue.

  • Sure. I was assuming that "this" is understood by context. However, does the question sound good to you? – Robert Smith Oct 24 '14 at 20:35

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