The difference between 'if' and 'when'

PUBLISHED : Thursday, 28 October, 2004, 12:00am
UPDATED : Thursday, 28 October, 2004, 12:00am

Some of you may be confused about the use of 'when' and 'if'.

These two little words are very important for joining two sentences together to say what will happen as a follow-up to something else happening.

Look at the following two sentences.

Tommy will go to Japan.

He has enough money.

They can be joined together and made into one sentence using both 'if' and 'when'. What is the difference?

1. Tommy will go to Japan WHEN he has enough money.

2. Tommy will go to Japan IF he has enough money.

'When' is a definite word. You are certain that something will happen when you use 'when'.

There is doubt in your mind when you use 'if'. Things might happen, but you are not certain. That is the difference between them.

You know that Tommy will soon have enough money and he will then go to Japan (sentence 1). We use 'when' to say that we expect something to happen.

Tommy might or might not have enough money but he will go to Japan if he does get enough money (sentence 2).

We use 'if' if we think it might happen but not for sure.

1. I will call you WHEN I get home tonight.

There is no doubt in your mind. You are certain. You know you will get home tonight so we will make the call.

2. I will call you IF I get home tonight.

Can you see the difference? There is some doubt in your mind that you might not get home tonight so you are saying that there is a chance that you might not be able to make the phone call.

Put 'if' or 'when' into these sentences.

I will call you _____ I've found my mobile phone. (certain)

2. Kit will be very angry _____ he finds out what you have done. (certain)

3. Yee will be very embarrassed _____ she finds out what you have said. (doubt)

4. I will be at the airport _____ your plane arrives. (certain)

5. I will wait inside the cinema _____ it starts raining. (doubt)

6. My hair will be blonde _____ you see me next month. (certain)

7. I will pass this exam _____ I work hard. (doubt)

8. Elsa will help you _____ you have problems. (doubt)

Which is better in these sentences, 'when' or 'if'? You must study closely at what the speaker wants to say.

9. He will go to university _____ he works hard.

10. You won't get sunstroke _____ you wear a hat.

11. I will arrive on time _____ the train is not late.

12. Mrs Ng will understand _____ you explain the situation to her. But she might not.

13. You will be rich _____ you get that new job. But I don't think your qualifications are good enough.

14. Do not use the lift _____ there is a fire.

15. I will meet you in town tonight _____ you want.

16. We will not go to the beach _____ the weather is too hot at the weekend.

17. I will buy you dinner on Saturday night _____ I have enough money.

18. We will go to Lamma this weekend _____ it's sunny.

Answers: 1, 2, 4, 6 - when; 3, 5, 7-18 - if