In many cases, if and whether can be used interchangeably without affecting the meaning.
| IF |
|---|
In the following situations, speakers prefer using IF.
|
| REPORTED SPEECH |
(I asked them, "Are you leaving?")
I asked them if they were leaving.
|
| SLIGHTLY LESS FORMAL |
I asked him if he is going to visit. (informal context)
(I asked him whether he would visit. (more formal)) |
| CONDITIONAL |
I asked him questions if he was not too busy.
I asked him questions when he was not too busy. |
| WHETHER | ||
|---|---|---|
In the following situations, speakers prefer using whether.
| ||
| WITH WORDS USED IN FORMAL CONTEXTS | ||
We inquired whether the President would attend the summit meeting. (investigate, explain, examine, study, decide, determine)
| ||
| WHEN STRESSED IN SPEECH | ||
We must ask ourselves whether we will accept failure.
| ||
| BEFORE "OR NOT" / REGARDLESS | ||
We are leaving whether you like it or not. (no option exists)
| ||
| DOUBT + "OR NOT" / ALTERNATIVE | ||
We don't know whether we are going or not. (doubt, can't say, be uncertain— about an alternative)
| ||
| BEFORE AN INFINITIVE | ||
We can't decide whether to leave or to stay.
| ||
| AFTER A PREPOSITION | ||
We were worried about whether you would like it.
| ||
| AFTER "THE QUESTION IS…" | ||
The main question is whether they are going also. (the problem is, the undecided point is)
| ||
| INITIAL POSITION / SUBJECT | ||
|
