If, Unless or When — Exercises on Choosing the Linking Word
Practice choosing between if, when and unless: possible versus certain events, and why unless already means 'if not'.
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___ you hurry, we'll miss the start of the film.
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Unless
'Unless' means 'if not' — we'll miss the start if you don't hurry. 'If you hurry' would say the opposite.
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___ the film ends, we can get something to eat.
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When
The film will definitely end, so 'when'. 'If' would suggest it might go on forever.
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___ you finish the course, you'll get a certificate — but a lot of people drop out.
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If
'A lot of people drop out' shows finishing isn't certain, so 'if'. 'When' would mean you're sure to get there.
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We can walk to the station ___ you're in a hurry — it's about twenty minutes.
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unless
'Unless' means 'if not' — twenty minutes is too slow for someone in a hurry, so walking is the plan only when you're not. With 'if', the sentence would say the opposite.
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We'll need to reschedule ___ Maria can't make it on Thursday.
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if
We only reschedule in the case that she can't come — that's 'if'. 'Unless' would mean we reschedule when she CAN come.
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I'll call you ___ I get home — I should be back by seven.
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when
'I should be back by seven' tells you getting home is certain, so 'when'. 'If' would suggest you might not get there at all.
If, Unless or When: Three Words, Three Claims
All three words introduce a condition and all three take the present simple, so the grammar does not tell you which to choose. The meaning does.
If presents the event as possible but uncertain. When presents it as certain, leaving only the timing open. The contrast is sharpest when both are grammatical: If I retire, I'll move to the coast is a plan contingent on something that may not happen, while When I retire, I'll move to the coast treats retirement as settled.
Unless means if not, and it carries its negative inside itself. We'll eat outside unless it's too cold means we will eat outside if it is not too cold. Two errors follow from missing this. The first is the double negative — unless you don't hurry — which reverses the sentence. The second is substituting if for unless, which also reverses it: We'll eat outside if it's too cold claims the opposite of the original.
Last updated: · Satori Editorial