what's the difference between wouldn't, shouldn't, shall and will?

Question

please explain. using the words is easy, but explaining why they're used in such ways is difficult. :)

Answer 1

"Wouldn't" and "will" are indicators of something a person is willing to do as opposed to his/her ability to do something (e.g. I can walk 3 miles, but I wouldn't do it when it's -30 degrees outside.). "Will" is also a directive (e.g. You will go to school tomorrow.).

Here is how Dictionary.com defines will/would as there are many ways to define them:
"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.”
–verb (used with object), verb (used without object) 10. to wish; desire; like: Go where you will. Ask, if you will, who the owner is."

"Shouldn't" and "shall" are used to identify something that a person is obliged to do or intends to do (e.g. I should go to class if I want to get a good grade. or I shall go to the movies tonight).

Answer 2

Wouldn't is used to describe something that you would not do, or something that is in your capacity to do but you refrain from doing it.
(ie, I wouldn't do that if I were you)

Shouldn't is used to describe something that you should not do because you feel it is wrong or is unjust, unfair or immoral on some level.
(You shouldn't cheat on your husband)

Shall is used to describe something you will do. It is definitely from the old english and it is less commonly used today. It was used to describe an action that one would undertake.
(ie, I shall challenge him to a duel!)

Will is the most common and is used to describe an action that you will take, as in you are sure you will be undertaking.
(ie, I will take out the trash)

Answer 3

OK: In the first person (I, we), use shall for normal discourse and will for emphasis. "I shall go to class tomorrow." "We WILL accomplish this."
In the second and third persons (you, he/she, they), it's the other way around: "He will come at 9." "You SHALL do this."
Should is used the same way as shall, and would the same way as would. "I should think not." "You wouldn't believe this." but "I WOULD not want to go." "You SHOULD get up on time."

Answer 4

wouldn't is something you absolutely would not do... Kill someone

shouldn't is something you shouldn't do, but still may...like eating a whole pizza by yourself....drinking too much..

shall is something you will do soon

I shall do my homework

Will is like the same as shall I think