Learn English @ Brooks Language: In case and if

in case and if

1 precautions
In case is mostly used to talk about precautions things which we do in order to be ready for possible situations.

I always take an umbrella in case it rains.

In clauses which refer to the future, in case is normally followed by a present tense (like most other conjunctions).

I’ve bought a chicken in case your mother stays to lunch.

2 in case and if

In British English, in case and if are normally used in quite different ways.

“I do A in case B happens” usually means “I do A first because B might happen later”. A is first.
“I do A if B happens” means “I do A if B has already happened.” B is first.
Compare:

Let’s buy a bottle of wine now because Roger might come later.
Let’s buy a bottle of wine if Roger comes. (= We’ll wait and see. If Roger comes, then we’ll buy a bottle of wine.
I’m taking an umbrella in case it rains.
I will open my umbrella if it rains.

In American English, in case can sometimes be used in the same way as if. In case the house burns down, we’ll get the insurance money. (GB If...)

Now do the test.

Ann might phone this evening. I don't want to go out _________ (in case/ if) she phones.

You should tell the police _________ (in case/ if) your bicycle is stolen.
I hope you'll come to London sometime. _________ (in case/ if) you come, you can stay with us.
This letter is for Susan. Can you give it to her _________ (in case/ if) you see her?
Write your name and address on your bag _________ (in case/ if) you lose it.
Go to the lost property office _________ (in case/ if) you lose your bag.
The burglar alarm will ring _________ (in case/ if) somebody tries to break into the house.
I’ve just painted the door. I'll put a WET PAINT notice next to it _________ (in case/ if) somebody doesn't realise it's just been painted.
I was advised to arrange insurance _________ (in case/ if) I needed medical treatment while I was abroad.

Answers:

in case