IF and whether are commonly used to join two sentences together and should be commonly used in both writing and speaking tests. Do you know the difference between them? If and whether are often interchangeable, but not always. Let’s look at under what condition we use “whether” and “if”.
We can use if or whether when 2 options are possible and if is used in a conditional sentence.
I don’t know whether/if Ling is still coming to dinner tonight.
2. Whether: to present two alternatives
It can be followed by the expression “or not”
I don’t know whether Liz will arrive or not.
With “if” we cannot use “or not”
The school board will meet to decide if they’re going to renovate the teaching building.
When “whether” can be used to start a clause that is the sentence subject or complement.
“Whether you come or not doesn’t matter.”
Whether is used before infinitive to express future plans
What we want to know is whether to go to the office tomorrow.
3. If: to introduce a condition
Use if to introduce a condition (i.e., in a conditional sentence). In a conditional sentence, a condition has to be satisfied before something occurs.
If there is a drop in house prices, I will consider buying.
The government would reduce taxes if they could afford it.