in case用作連詞時有以下兩個用法：

1. 表示條件，意為“如果”“萬一”。如：

In case it rains, do not expect me. 如果下雨，就不要等我了。

In case you see him, ask him about it. 如果你見著他，問問他這事。

In case I forget, please remind me of my promise. 如果我忘了，請提醒我我的諾言。

In case he arrives before I get back, please ask him to wait. 如果他在我回來之前到，請讓他等等我。

2. 表示目的，意為“以防”“生怕”。如：

I’m shy of buying shares in case I lose money. 我不敢買股票，怕賠錢。

Take warm clothes in case the weather is cold. 帶些暖和的衣服，以防天氣變冷。

I’ll keep a seat for you in case you should change your mind. 我給你留一個座位，以防你會改變主意。

We took our swimming things in case we happened to find a pool. 我們帶上游泳用品，以備萬一能找到一個水池。

注：有時中間的謂語由 should構成，強調偶然性，可譯為“萬一”：

I wrote down her address in case I should forget it. 我寫下了她的地址，以防萬一我忘了。

I always slept by the phone in case he should ring during the night. 我總是睡在電話機旁邊，怕萬一他夜間打電話來。