Could you explain the difference between "When do you think he will come?" and "How do you think when will he come?". Why only the first one is grammatically correct and the second is wrong? Why can't I start it with how?

  • Because how asks for a method, and when asks for a time. If you have a question of time, use when. It's the same as asking Why do you think when he will come? is a different (wrong) question. Adding words changes things. One nitpick though: it's not ungrammatical. It's actually a perfectly grammatical sentence. It's just the semantics are wrong, it's meaningless. But nothing wrong with the grammar. You might simply say it's "unidiomatic" (i.e. not a thing a native speaker would ever say).
    – Dan Bron
    Commented Oct 20, 2018 at 16:15

1 Answer 1


You are trying to translate the Russian "Как ты думаешь, когда он придет".

But you are doing it word-for-word. That is not how translation works. Not in this case, not in general. Doing that will always get you in trouble.

The English equivalent for "Как ты думаешь" is "what do you think", not "*how do you think". Or maybe "what do you figure", or "what would you say", or "what's your opinion" even. Or any number of others, really. But definitely not "*how do you think".

"How do you think" in English can be grammatical, but then it has a different meaning entirely. It is literally asking about the physical and chemical mechanisms and processes in the brain that we call thinking. The Russian equivalent to that would be something along the lines of "каким образом ты думаешь" or "как работает мыслительный процесс", or what have you.

So what you are asking in English, right now, is "Как работает твоя голова, когда он объявится?" Needless to say, that's a very funny question.

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