in case

  • We use in case to talk about things we do because something else might happen.
      Take an umbrella in case it rains. (= . . . because it might rain.)
      I’ve bought a chicken in case your mother stays to lunch.
      I wrote down her address in case I forgot it.

    After in case, we use a present tense with a future meaning.

      . . . in case it rains. (NOT . . . in case-it-will rain.)

    We can also use should + infinitive. In this structure, should means ‘might’.

      I’ve bought a chicken in case your mother should stay to lunch.
      I wrote down her address in case I should forget it.

    The structure with should is more common in the past.

  • Don’t confuse in case and if.
      ‘I do A in case B happens’ =
      ‘I do A first because B might happen later.’ A is first.
      ‘I do A if B happens’ =
      ‘I do A if B has happened first.’ B is first.

    Compare:

      Let’s get a bottle of wine in case Roger comes.
      (= We’ll buy some 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 the wine. If he doesn’t we won’t.).