If introduces a condition or, in its second use, means whether. In the first meaning, it says what has to happen: If it rains, we'll stay in. In the second, it comes after know, ask, wonder or not sure: I wonder if she's free means I wonder whether she's free.
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If + present, + will/can + verb; clause + if + clause; know/ask/wonder/not sure + if + clause (= whether)
- If the train is late again, I'll take a taxi to the airport.
- If you need the slides, I can send them to you after the meeting.
- I'm not sure if my manager will approve an extra day off next week.
What changed
First versionIf it will rain tomorrow, we'll stay at home and watch a film.
RevisionIf it rains tomorrow, we'll stay at home and watch a film.
When the condition is in the future, will after if seems logical: the rain is tomorrow, after all. But after if meaning “on condition that”, English talks about the future in the present tense: if it rains. Will stays in the other half: we'll stay at home.
When if means whether, the will rule doesn't apply: it's no longer a condition but a question about the future. I don't know if she will come. You can recognise this if by the word before it: know, ask, wonder, not sure. In essays, whether is more common in this meaning: It is unclear whether the new tax will reduce traffic.
Your turn
Text me if your train ___ late tonight, and I'll pick you up from the station.
Show the answer
is — Here if introduces a condition: text me in case the train is late. In a condition about the future, English uses the present tense, so is. Will be would only fit if meaning whether: I don't know if it will be late.
Write to a colleague about what you'll do if something goes wrong tomorrow. After if, name one possible problem, then say what you'll do.
If the client cancels tomorrow's call, I'll use the time to finish the budget report.
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