Unless means “if not” or “except if”. It introduces the condition under which something will not happen: I'll come unless it rains, that is, I'll come if it doesn't rain. The negative is already built into the word, so the verb after “unless” is positive. To talk about the future after “unless”, use the present tense: unless it rains, not unless it will rain.
How would you use unless?
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clause + unless + clause; Unless + clause, + clause; unless + present simple (about the future)
- Traffic in large cities will not improve unless public transport becomes cheaper and more reliable.
- Unless students receive regular feedback, they tend to repeat the same mistakes.
- I'll be there by seven unless my flight is delayed.
What changed
First versionWe'll miss the train unless we don't leave now.
RevisionWe'll miss the train unless we leave now.
Because “unless” means “if not”, it is easy to add another “not” after it: unless we don't leave. But the negative is already in “unless”, and a second one reverses the meaning. So “don't” is removed: unless we leave.
“Unless” can usually be replaced with “if … not”: unless we leave now = if we don't leave now. The reverse does not always work. When the main part of the sentence is about feelings, a reaction to something that may not happen, you need “if … not”: I'll be surprised if he doesn't come. You cannot say I'll be surprised unless he comes.
Your turn
You won't be allowed into the exam ___ you bring your passport.
Show the answer
unless — Without a passport, you will not be let into the exam, so the condition is negative: “if you don't bring it”. That is exactly what “unless” means. With “if”, the meaning would be the opposite: you would not be allowed in if you brought your passport.
Write about your plans for the weekend. Say what you are going to do and, after unless, name one thing that could stop you.
I'm going to cycle to the lake on Saturday unless it's too windy.
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