English grammar and usage of if

An analysis of the usage of "whether" and "if"

First, the similarities.

1. when and if can lead to object clauses, which are often placed after verbs such as see, ask, learn, tell, wonder, question and find.

He asked me where I could help him. I wonder where/whether he lives there.

Both "where" and "if" can be used as formal subject clauses. For example, it is my uncle who is here tonight.

After BEUNCERTAIN/DOBTFUL, WHERE is often used to guide the object clause, and sometimes if can be used, such as: We are UNCERTAIN WHERE/IF Mary is coming.

Second, differences.

1.Where can be placed at the beginning of a sentence to guide the subject clause, but if can't. It is not known that the 2000 Olympic Games will be held in Beijing. The answer is C.

2.When can be used to guide object clauses after prepositions, but If not. Success depends on where we work hard.

3.Where can guide predicative clauses, but if can't. For example, the problem is not worth doing.

4. When leading appositive clauses after nouns, use when instead of if. It is up to the teacher to decide when the students should answer the correct questions.

5.When can be followed by infinitive, if not. Please tell us where to go or stay here.

6. After some verbs (such as discuss), you can only use wheel instead of if to guide the object clause. We discussed when to close the door.

7. When introducing the negative concept in the object clause, you can only use if instead of what. For example, he asked me if I had finished my work.

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Both "when" and "if" can lead to object clauses, indicating "whether" and can be used interchangeably in spoken or indirect speech. For example:

I wonder if I can get some advice from you.

Ask him if he can come.

But in some cases, the usage of "when" and "if" is different.

1 guided clause. "whether" can often be used directly with "whether", but "if not". For example:

Let me know if you can come.

Let me know if you can come.

Whether the object clause refers to the beginning of a sentence can only be guided by what, not by if. For example:

Whether it is true or not, I can't say.

Whether it is true or not, I can't say.

3.Where can use to guide infinitives, but if can't. For example:

I don't know what to accept or reject.

I don't know whether to accept or refuse.

4.What and its leading elements can be placed after preposition as the object of preposition, but if can't. For example:

I'm afraid I hurt her feelings.

I'm worried about whether I hurt her feelings.

5.Where can lead clauses to be subject, predicative or appositive, but if can't. For example:

I'm not sure where he will come.

Whether he will come is uncertain.

His first question was when Tom arrived.

His first question is whether Tom has arrived.

We must consider the question of where to take measures.

We must consider whether to take these measures.