一人称叙述文 will 今自分ですると決めたこと
In the 1st person descriptive, ‘will’ means your determination you’ve made on the spot.
I will go to graduate school. I’ve determined this just now.
一人称叙述文 am going to 前からすると決まっていたこと
In the 1st person descriptive ‘am going to’ means your plan you scheduled earlier.
I’m going to go to graduate school. I decided this last year.
二人称/三人称叙述文 will 予想
In the 2nd or 3rd person descriptive, ‘will’ means your prediction.
You will surely be admitted to graduate school.
He will surely be admitted to graduate school.
二人称疑問文 will 依頼
In the 2nd person interrogative, ‘will’ means your request.
Will you open the window?
三人称疑問文 予想
In the 3rd person interrogative, ‘will’ means your prediction.
Will it be rainy tomorrow?
Will he also be admitted to graduate school?
二人称/三人称疑問文叙述文 be going to 意志
In the 2nd or 3rd person interrogative or descriptive, ‘be going to’ means your, his or her own plan or determination.
Are you going to go to graduate school?
Yes, I am!
Is she also going to go to graduate school?
Probably.
