- Do you know that he will be our coach?
- Do you know if he will be our coach?
I think both sentences are grammatically ok, just meaning two different things.
In the first sentence, it's decided that 'he' will be the coach and the intention of the question is to see if the listener knows the information.
and in the second, the speaker is not sure if 'he' will be the coach, and wants to ask the listener about it.
Do I understand the sentences right?
Best Answer
You're exactly right. Both are grammatically correct, with slightly different meanings.
"Do you know if he will be our coach?" definitely implies that the speaker does not have any information, and is asking the listener.
"Do you know that he will be our coach?" when written down suggests it's a fact that he's going to be our coach, but asks whether the listener knows that information.
When spoken, emphasis/inflection can change the meaning.
"Do you know that he will be our coach?" suggests the speaker is asking the listener to confirm how reliable the information is. Do you know this or are you just guessing?
"Do you know that he will be our coach?" suggests everyone else knows already, and the speaker is asking if the listener is also aware (the meaning you described).
Perhaps clearer: "He will be our coach. Did you know that?" or "I heard he will be our coach. Do you know if that's true?"