In Case vs. If
- I always take an umbrella in case it rains. (= because it might rain.)
After in case, we use a present tense to refer to the future.
We often use should + infinitive after in case. This adds the meaning by chance. This structure is common in sentences about the past.
- I wrote down her address in case I should forget it.
In case and if
In British English, in case and if are used in quite different ways.
- Let us buy a chicken in case Peter comes. (=Let us buy a chicken now because Peter might come later.)
- Let us buy a chicken if Peter comes. (=We will wait and see. If Peter comes, then we will buy the chicken. If he doesn’t we won’t.)
In American English, in case can sometimes be used in the same way as if.
The prepositional phrase in case of is often used in similar situations to if.
- In case of fire, break glass. (=If there is fire …)