What is the difference between the following sentences -

1) The train will arrive in 10 minutes.

2) The train arrives in 10 minutes.

3) The train is arriving in 10 minutes.

I have seen all the 3 sentences being used.What is the exact meaning and in which situation are they used?

I have also seen a sentence like this -

The surgeon will have operated on 6 patients before she attends a luncheon meeting.


Can i use "before she will attend a luncheon meeting." If yes,what will be the difference between the 2 sentences. If no, why cant I use it?
In any expected circumstance (at the station, on the platform, in the taxi going there, etc), all three sentences mean the same. With only 10 minutes to go, I can see few other situations in which you would use these.

The surgeon will have operated on 6 patients before she attends a luncheon meeting.-- We normally simplify the verb in the dependent clause, most frequently from future to present, as here. It is so frequent that will would sound odd here.
I'll butt in, if I may. The future tense would be incorrect in a subordinate clause denoting time or condition:
I'll do it before he comes. (Not: will come)
I'll do it after he comes. I'll do it when he comes. I'll do it if he comes.
The answer to your second questions is: yes.
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Thanks for your response.I have some more questions.

You have mentioned that using a future tense in the dependent clause would sound odd.But is it grammatically correct?is it correct usage?

Also,in the first 3 sentences,what if "10 minutes" changes to 5 hours or 2 days?Will the sentences still be correct and have the same meaning?
 Cool Breeze's reply was promoted to an answer.
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