条件性动词 (Conditional Clauses) – will, shall, would, should
汉语文法没有条件性动词，用汉语表达同样的意思需要用上下文来限定或补充句子的意思。
Will 和 Shall 有和不同？
1. We use “will” to predict a future event. For example:
无条件: Jane will buy a new purse.
有条件：John will go to Japan if he has the money.
2. We use “shall” to imply a command or an order.
“shall” 有“必定”，“应该”或“必须”的含义。例子：
Jane shall eat her breakfast. (It means Jane is being commanded to eat her breakfast.)
ABC Enterprises shall execute the terms of the agreement.
3. We use “shall” to promise something. Example:
I shall read the book you gave me.
4. We use “shan’t” for “shall not”. Example:
英国人喜欢用 ”shall” 和 “shan’t”. 在美国
I shan’t be going to your party after all.
和
I won’t be going to your party after all
有同样的意思。
Will 和 Would 有和不同？
5. We use “will” to show that something is actually going to happen (see example 1 above), or is still happening.
We use “would” when the event is more tentative, or is in the past. (“Would” 表示事情存有不肯定性，也可以表示过去时态。) For example:
By September I will have served 3 years in the army. (It implies you are still in the army.)
By September I would have served 3 years in the army. (It implies you are no longer in the army.)
I will help if asked. (It means you will definitely help.)
I would help if asked. (It means you may or may help, and you may or may not be asked.)
Should 的用法
Should 有“应该”的意思。 Example:
6. Mom should see the doctor for her condition.
Use of “will have” and "would have" to mean “want”. Example:
7. At the restaurant, Bob was asked by the waiter, “what would you like, Sir.” Bob answered, “I’ll have some salad.”
Notice the waiter does not say, “What do you want?”, and Bob does not answer, “I want salad.” The form of speech used in the example above is more elegant.
