A reader writes:
“… what’s the difference between shall and will?”
We will present here only the auxillary verb forms (“will” can also be a noun).
Bottom line: use shall when first person (I or we) is the subject of future action. Use will when the subject is second or third person. Of course, there are exceptions.
There is a great write-up on “shall vs. will” at Bartleby.com [The American Heritage® Book of English Usage]. (Click here to read the traditional rules and the reality)
shall. auxillary verb. past tense should (shŏŏd). Used before a verb in the infinitive to show:
1. Something that will take place or exist in the future: We shall arrive tomorrow.
2. Something, such as an order, promise, requirement, or obligation: You shall leave now. He shall answer for his misdeeds. The penalty shall not exceed two years in prison.
3. The will to do something or have something take place: I shall go out if I feel like it.
4. Something that is inevitable: That day shall come.
will. auxiliary verb. past tense would (wŏŏd).
1. am (is, are, etc.) about or going to: I will be there tomorrow. She will see you at dinner.
2. am (is, are, etc.) disposed or willing to: People will do right.
3. am (is, are, etc.) expected or required to: You will report to the principal at once.
4. may be expected or supposed to: You will not have forgotten him. This will be right.
5. am (is, are, etc.) determined or sure to (used emphatically): You would do it. People will talk.
6. am (is, are, etc.) accustomed to, or do usually or often: You will often see her sitting there. He would write for hours at a time.
7. am (is, are, etc.) habitually disposed or inclined to: Boys will be boys. After dinner they would read aloud.
8. am (is, are, etc.) capable of; can: This tree will live without water for three months.
9. am (is, are, etc.) going to: I will bid you “Good night.”
Source: Dictionary.com. (see usage note)