DIFFERENCE BETWEEN IF AND IN CASE.

Many people think IF and IN CASE have the same meaning. Most of them are able to use IF correctly but they are confused about the accurate use of IN CASE. Look at the following sentences:

(1) I will buy some meat IF Jane comes.
(2) I will buy some meat IN CASE Jane comes.

Are these two sentences the same in meaning? No! According to the first sentence, I will buy meat only after Jane’s coming. In other words, Jane will come first then I will buy meat (otherwise I will not buy). To make it more clear, [Jane’s coming first] and [meat-buying later]

The second sentence means, I will buy meat before Jane’s coming. It means, I am going to buy some meat first as I expect Jane but it does not matter whether Jane will come or not later. In short, [meat-buying first] and [Jane’s coming later].

One important thing to note here is, the if-clause can come either at the beginning of a sentence or at the last. Look at the following constructions:

I will buy some meat IF Jane comes (correct)
IF Jane comes, I will buy some meat (correct)

However, this inversion is not possible with IN CASE-clause. Compare:

I will buy some meat IN CASE Jane comes (correct)
IN CASE Jane comes, I will buy some meat (incorrect)

More examples:
I will wear a helmet IF an accident occurs. (..will wear helmet after accident)

I will wear a helmet IN CASE an accident occurs. (..will wear helmet in advance as a precaution)

I will carry the charger IF the mobile’s battery runs down. (will carry charger after battery is low)

I will carry the charger IN CASE the mobile’s battery runs down. (..will carry charger in advance as a precaution)