Study this example situation:
Your car should have a spare tire because it is possible you will have a flat tire.
Your car should have a spare tire in case you have a flat tire.
In case you have a flat tire = because it is possible you will have a flat tire.
Some more examples of in case:
– I’ll leave my cell phone on in case Jane calls. (= because it is possible she will call)
– I’ll draw a map for you in case you can’t find our house. (= because it is possible you won’t be able to find it)
– I’ll remind them about the meeting in case they’ve forgotten. (= because it is possible they have forgotten)
We use just in case for a smaller possibility:
– I don’t think it will rain but I’ll take an umbrella just in case. (= just in case it rain)
Do not use will after in case. Use a present tense for the future (see Unit 24):
– I’ll leave my phone on in case Jane calls. (not in case Jane will call)
In case is not the same as if. We use in case to say why somebody does (or doesn’t do) something.
You do something now in case something happens late.
- We’ll buy some more food in case Tom comes.
(= Maybe Tom will come; we’ll buy some more food now, whether he comes or not; then we’ll already have the food if he comes.)
- I’ll give you my phone number in case you need to contact me.
- You should register your bike in case it is stolen.
- We’ll buy some more food if Tom comes.
(= Maybe Tom will come; if he comes, we’ll buy some more food; if he doesn’t come, we won’t buy any more food.)
- You can call me at the hotel if you need to contact me.
- You should inform the police if your bike in stolen.
You can use in case + past to say why somebody did something:
– I left my phone on in case Jane called.
(= because it was possible that Jane would call)
– I drew a map for Sarah in case she couldn’t find the house.
– We rang the doorbell again in case they hadn’t heard it the first time.
In case of is not the same as in case. In case of … = if there is … (especially on sings, etc.):
– In case of fire, please leave the building as quickly as possible. (= if there is a fire)
– In case of emergency, call this number. (= if there is an emergency)