Study these examples:
A: What time will you phone me tomorrow?
B: I'll phone you when I get home from work.
'I'll phone you when I get home from work' is a sentence with two parts:
the main part: 'I'll phone you' and the when-part: 'when I get home from work (tomorrow)'
The time in the sentence is future ('tomorrow') but we use a present tense (get) in the when part of the sentence.
We do not use will in the when-part of the sentence:
* We'll go out when it stops raining. (not 'when it will stop')
* When you are in London again, you must come and see us. (not 'when you will be')
* (said to a child) What do you want to be when you grow up? (not 'will grow')
The same thing happens after: while before after as soon as until or till
* I'm going to read a lot of books while I'm on holiday. (not 'while I will be')
* I'm going back home on Sunday. Before I go, I'd like to visit the museum.
* Wait here until (or till) I come back.
You can also use the present perfect (have done) after when/after/until/as soon as:
* Can I borrow that book when you've finished it?
* Don't say anything while Ian is here. Wait until he has gone.
It is often possible to use the present simple or the present perfect:
* I'll come as soon as I finish. or I'll come as soon as I've finished.
* You'll feel better after you have something to eat. or You'll feel better after you've had something to eat. But do not use the present perfect if two things happen together. The present perfect shows that one thing will be complete before the other (so the two things do not happen together).
Compare:
* When I've phoned Kate, we can have dinner. (= First I'll phone Kate and after that we can have dinner.)
but * When I phone Kate this evening, I'll invite her to the party. (not 'when I've phoned') (In this example, the two things happen together.)
After if, we normally use the present simple (if I do/if I see etc.) for the future:
* It's raining hard. We'll get wet if we go out. (not 'if we will go')
* Hurry up! If we don't hurry, we'll be late.
Compare when and if:
We use when for things which are sure to happen:
* I'm going shopping this afternoon. (for sure) When I go shopping, I'll buy some food.
We use if (not 'when') for things that will possibly happen:
* I might go shopping this afternoon. (it's possible) If I go shopping, I'll buy some food.
* If it is raining this evening, I won't go out. (not 'when it is raining')
* Don't worry if I'm late tonight. (not 'when I'm late')
* If they don't come soon, I'm not going to wait. (not 'when they don't come')
EXERCISES
25.1 Complete these sentences using the verbs in brackets. All the sentences are about the future. Use will/won't or the present simple (I see/he plays/it is etc.).
1. I'll phone (phone) you when I get (get) home from work.
2. I want to see Margaret before she --- (go) out.
3. We're going on holiday tomorrow. I --- (tell) you all about it when we --- (come) back.
4. Brian looks very different now. When you --- (see) him again, you --- (not/recognise) him.
5. We must do something soon before it --- (be) too late.
6. I don't want to go without you. I --- (wait) until you --- (be) ready.
7. Sue has applied for the job but she isn't very well qualified for it. I --- (be) surprised if she --- (get) it.
8. I'd like to play tennis tomorrow if the weather --- (be) nice.
9. I'm going out now. If anybody --- (phone) while I --- (be) out, can you take a message?
25.2 Make one sentence from two.
1. You will be in London again. You must come and see us then.
You must come and see us. when you are in London again.
2. I'll find somewhere to live. Then I'll give you my address.
I --- when ---
3. I'll do the shopping. Then I'll come straight back home.
--- after ---
4. It's going to start raining. Let's go home before that.
--- before ---
5. She must apologise to me first. I won't speak to her until then.
--- until ---
25.3 Read the situations and complete the sentences.
1. A friend of yours is going to visit London. You want to know where she is going to stay.
You ask: Where are you going to stay when _you are in London?_
2. A friend of yours is visiting you. She has to go soon but maybe there's time for a cup of tea.
You ask: Would you like a cup of tea before ---?
3. Your friend is reading the newspaper. You'd like it after her.
You ask: Can I have the newspaper when ---?
4. You want to sell your car. Jim is interested in buying it but he hasn't decided yet.
You ask: Can you let me know as soon as ---?
5. There are serious traffic problems in your town but they are building a new road.
You say: I think it will be better when ---.
25.4 Put in when or if.
1. Don't worry _if_ I'm late tonight.
2. Tom might phone while I'm out this evening. --- he does, can you take a message?
3. I'm going to Rome next week. --- I'm there, I hope to visit a friend of mine.
4. I think Jill will get the job. I'll be very surprised --- she doesn't get it.
5. I'm going shopping. --- you want anything, I can get it for you.
6. I'm going away for a few days. I'll phone you --- I get back.
7. I want you to come to the party but --- you don't want to come, that's all right.
8. We can cat at home or, --- you prefer, we can go to a restaurant.
25.1
2 goes
3 will tell/'ll tell ... come
4 see ... won't recognise/will not recognise
5 is/'s
6 will wait/'ll wait ... are/'re
7 will be/'ll be ... gets
8 is
9 phones ... am/'m
25.2
2 I'll give you my address when I find somewhere to live. or ... when I've found somewhere to live.
3 I'll come straight back home after I do the shopping. or ... after I've done the shopping.
4 Let's go home before it starts raining.
5 I won't speak to her until she apologises. or ... until she has apologised.
25.3
2 you leave/you go
3 you finish with it/when you finish reading it or you've finished with it you've finished reading it you've read it
4 you decide/you've decided
5 they finish the new road or they've finished the new road or they've built the new road
25.4
2 If 3 When 4 if
5 If 6 when 7 if 8 if
