If you will have dinner at home, tell me.
or
If you have dinner at home, tell me.
What is the difference between the two sentences? Which one sounds natural?
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Sign up to join this communityIf you will have dinner at home, tell me.
Here "will" is used with the (slightly archaic) meaning of "wish/intend to", so the sentence is correct, but modern English speakers would generally use "wish/want/intend to" instead, or "would like to".
If you have dinner at home, tell me.
This is a simple sentence that requests you to tell the speaker if you actually have dinner at home, so it is also grammatically correct but conveys a totally different meaning.
I think the second one is correct.
If you have dinner at home, tell.
Although this Source states:
When the situation or action depicted in the if-clause is a result of the main clause, the will-future is used in the if-clause.
He'll pay me $10 if I'll help him do the dishes. (Doing the dishes is the result of paying ten dollars.)
So in any other case, you would not have will/would in an if clause.
In your case, telling him is not the result of having dinner at home, but of planning to have dinner at home.
I hope this explains it correctly.