21
单元 21: When and if
Unfinished conditional sentences
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- 1Go beyond intermediate with our new video course
- 2Reported speech in 90 seconds!
- 3If or whether?
- 45 ways to use 'would'
- 5Let and allow
- 6Passive voice
- 7Unless
- 8Mixed conditionals
- 9The zero article - in 90 seconds
- 10The indefinite article - in 90 seconds
- 11The. That's right - the! Learn all about it in 90 seconds
- 12The continuous passive
- 13Future perfect
- 14Need + verb-ing
- 15Have something done
- 16Wish
- 17Word stress
- 18Different ways of saying 'if'
- 19Passive reporting structures
- 20The subjunctive
- 21When and if
- 22Inversion
- 23Phrasal verbs
- 24The future
- 25Modals in the past
- 26Narrative tenses
- 27Phrasal verb myths
- 28Conditionals review
- 29Used to - review
- 30Linking words of contrast
Grammar Reference
When and if
The main difference is to do with certainty. Compare these:
1) If the coin lands on tails, I'll eat these sweets.
2) When the coin stops, I'll know what to do.
In the first sentence, we don't know what will happen. The coin could land on heads or tails. Both consequences are possible, so we use if.
But in the second sentence, we are certain that the coin will stop. It's a question of when it stops, not if it stops.
