[求助] whether/if 作从句引导词的异同总结（语法知识点上找不到）

谢了

1.  indirect quesitons
We can generally use both whether  and if   to introduce indirect yes/no  questions.
I'm not sure whether/if  I'll have time.
I asked whether/if  she had any letters for me.

After some verbs, whether  is preferred to if.
We discussed whether  we should close the shop.

In a formal style, whether  is usually preferred in a two - part question with or.
Let me know whether  you can come or  not.  (....if you can come or not  is also possible.)
The directors have not decided whether  they will recommend a dividend or  reinvest the profits.

If an indirect question is fronted, whether  is used.
Whether  I'll have time I'm not sure at the moment.

2.  prepositions
After prepositions, only whether  is possible.
There was a big argument about whether  we should move to a new house.  (NOT....about if we should move...)
I haven't settled the quesiton of whether I'll go back home.  (NOT....quesiton of if...)

3. infinitives
Whether, but not if,   is used before  to - infinitives.
THey can't decide whether to get  married now or wait.  (NOT they can't decide if to get married...)

4.  subject, complement and adverbial clauses
When a question-word clause is a subject or complement, whether  is normally preferred.
Whether we can stay with my mother  is another matter.  (subject)
The quesiton is whether the man can be trusted.  (complement)

If  is sometimes possible in a very informal style.
The quesion is if the man can be trusted.
Whether you like it or not, I'm staying here.
    

HTH (Hope that helps)

可不可以這樣理解：

從語法上看，能用if的地方就能用whether，而能用whether的地方不一定能用if，whether比if範圍更廣，因此在兩個選項一個用if另一個用whether而其他部分全一樣時，選擇whether是最保險的