"will" and "be going to" interchangeable ?

[ph2004]

Are "will" and "be going to" interchangeable ? For instance "I'm going to leave tomorrow/I'll leave tomorrow" and "What are you going to get ?/What will you get ?" Are all sentences correct ?

 

[Khosro]

Are "will" and "be going to" interchangeable ? For instance "I'm going to leave tomorrow/I'll leave tomorrow" and "What are you going to get ?/What will you get ?" Are all sentences correct ?

They are not usually interchangeable.

Please complete your second sentence. get what? what do you want to say with this sentece?

About your first sentence. Read the following sentences:
1- "Ann is in hospital." "Oh really? I didn't know. I'll go and visit her."
2- "Ann is in hospital." "Yes, I know. I'm going to visit her tomorrow."

We use "will" when we decide to do something at the time of speaking.The speaker has not decided before. In sentence 1 she has not decided before to go to hospital.

We use "be going to" when we have already decided to do something. In sentence 2 she has already decided to go to hospital. She already knows that Ann is in hospital.

But sometimes there is not much difference between will and going to. For example, you can say:
I think the weather will/going to be nice tomorrow.