A when sentence has two parts and either can come first; put a comma after the when part if it comes first. The same goes for before, while and after. When the meaning is future, use the present after when, before, while, after and until: when I get home, not when I will get home.
A Two parts, either order
When I left the house, it was snowing.
This sentence has two parts: when I left the house (part A) and it was snowing (part B). Either part can come first.
Put a comma after part A when it comes first.
- When I left the house, it was snowing.
- It was snowing when I left the house.
- When you feel sleepy, don't drive.
- Don't drive when you feel sleepy.
- Max was delighted when he got the job.
- When Max got the job, he was delighted.
B before, while, after
before, while and after work the same way, with the same comma rule.
- Always check your mirrors before you pull out.
- Before you pull out, always check your mirrors.
- While I was waiting for the train, it started to hail.
- It started to hail while I was waiting for the train.
- She never rode a horse again after she fell off.
- After she fell off, she never rode a horse again.
C Present tense for the future
Next month Tom is going to Rome. His friend Ana lives in Rome, but she is going to Peru next month. So they will not meet.
Ana will be in Peru when Tom is in Rome.
The time is future, but after when we use the present: when Tom is in Rome (not when Tom will be).
The same applies after before, while, after and until.
- When I get home tonight, I'm going to have a bath. (not When I will get home)
- I'm busy now. I'll ring you later when I have a minute.
- Please lock the door before you leave. (not before you will leave)
- Our neighbour is going to feed the cat while we're on holiday. (not while we will be)
- I'll wait here until you get back. (not until you will get back)
Exercises
98.1 Make sentences beginning with When. Join one part from each list. List A: I went out / I'm tired / I rang her / I go on holiday / the film ended / I got to the hotel. List B: I switched off the TV / I always book the same cottage / there were no rooms / it was raining / there was no answer / I like to watch TV.
When I went out ...
When I went out, it was raining.
When I went out, it was raining.
When I'm tired ...
When I'm tired, I like to watch TV.
When I rang her ...
When I rang her, there was no answer.
When I go on holiday ...
When I go on holiday, I always book the same cottage.
When the film ended ...
When the film ended, I switched off the TV.
When I got to the hotel ...
When I got to the hotel, there were no rooms.
98.2 Complete the sentences. Choose from the box: somebody broke into the flat / before they crossed the street / they moved to Australia / before they lived here / while they were away / when they heard the news / they didn't believe me.
somebody broke into the flatbefore they crossed the streetthey moved to Australiabefore they lived herewhile they were awaywhen they heard the newsthey didn't believe me
They looked left and right before they crossed the street.
They looked left and right before they crossed the street.
They were really shocked .
They were really shocked when they heard the news.
After they retired, .
After they retired, they moved to Australia.
The parcel was delivered .
The parcel was delivered while they were away.
Where did they live ?
Where did they live before they lived here?
While they were asleep, .
While they were asleep, somebody broke into the flat.
When I told them what had happened, .
When I told them what had happened, they didn't believe me.
98.3 Which is right? Choose the correct form for each gap.
I'll stay here until you come back. (I stay / I'll stay) (come / will come)
I'll stay here until you come back.
I'll ring you back when I my shift. (finish / 'll finish)
I'll ring you back when I finish my shift.
We need to act before too late. (it's / it will be)
We need to act before it's too late.
Our teacher is retiring this year. really miss her when . (We / We'll) (she goes / she'll go)
Our teacher is retiring this year. We'll really miss her when she goes.
Stay inside for now. Wait until the hail . (stops / will stop)
Stay inside for now. Wait until the hail stops.
and see you when in Bath again. (We come / We'll come) (we're / we'll be)
We'll come and see you when we're in Bath again.
When round tomorrow, the photos. (I come / I'll come) (I bring / I'll bring)
When I come round tomorrow, I'll bring the photos.
I'm going to Lisbon next month. I hope to visit some old friends while there. (I'm / I'll be)
I'm going to Lisbon next month. I hope to visit some old friends while I'm there.
"Don't forget to give me your new number." "OK, it to you before ." (I give / I'll give) (I go / I'll go)
"Don't forget to give me your new number." "OK, I'll give it to you before I go."
98.4 Use your own ideas to complete these sentences. The answers below are examples; yours will be different.
Can you turn off the light before ...?
Example answer: Can you turn off the light before you go out?
What are you going to do when ...?
Example answer: What are you going to do when you leave school?
When I have more time, ...
Example answer: When I have more time, I'm going to learn the piano.
I'll wait for you while ...
Example answer: I'll wait for you while you get changed.
When I start my new job, ...
Example answer: When I start my new job, I'll have to get up earlier.
Will you be here when ...?
Example answer: Will you be here when I get back?