Learning English Grammar | When do I use when, if and whether?

English Grammar | how to use when, if and whether

Many people would stop using their cars when public transport was better. [incorrect]
Many people would stop using their cars if public transport was better. [correct]

We discussed if universities should charge tuition fees. [incorect]
We discussed whether universities should charge tuition fees. [correct]

We use when to talk about an event or situation that we believe will happen:
  • I plan to go travelling when I finish my studies. [I expect to finish.]
    Give me a call when you arrive at the airport. [We expect the person to arrive.]

We use if to talk about a hypothetical possibility, especially in conditional sentences:
  • I would only go home if it was a real emergency.
    Give me a call if there are any problems. [Problems are a possibility, but not expected]

We also use if in certain polite requests:
  • I would appreciate it if / would be grateful if you could call me back.
    Would you mind if I asked you a few questions about the accident?

We use whether where we are considering two possibilities:
  • I don’t know whether to have beef or chicken for dinner.
    Many students have to get a part-time job whether or not they want to.

We use whether after certain verbs (and nouns) which involve considering two options:
  • They had a meeting to discuss whether they should take further action.
    The current debate is whether immigrants should adopt local customs.

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