某事很可能發(fā)生,條件是可能存在的,主句中某種情況發(fā)生的概率也是很高的.如：
If you ask him,he will help you．如果你請他幫忙,他會幫你的.
If you fail in the exam,you will let him down．如果你考試不及格,你會讓他失望的.
If you have finished the homework,you can go home．如果你作業(yè)做完了就可以回家了.
另外,if從句還表示不可實現(xiàn)的條件或根本不可能存在的條件,也就是一種虛擬的條件或假設(shè).從句多用一般過去時或過去完成時,表示對現(xiàn)在或過去的一種假設(shè).如：
If I were you,I would invite him to the party．如果我是你,我會邀請他參加聚會.
I would have arrived much earlier if I had not been caught in the traffic．要不是交通堵塞,我本會來得早一些.
另外你還要注意if 條件句的時態(tài)搭配
1．if從句用一般現(xiàn)在時,主句用一般將來時
If he runs he’ll get there in time.如果他用跑的,他就會及時趕到那兒.
The cat will scratch you if you pull her tail.如果你拉貓的尾巴,它就會抓你.
2．if從句用一般現(xiàn)在時,主句用may/might/can
If the fog gets thicker the plane may/might be diverted.如果霧在大一些,飛機可能就會改在別的機場降落.
If it stops snowing we can go out.如果雪停了,我們就可以出去.
3．if從句用一般現(xiàn)在時,主句用must/should
If you want to lose weight you must/should eat less bread.如果你想減肥,你必須少吃面包.
4．if從句用一般現(xiàn)在時,主句用一般現(xiàn)在時
If you heat ice it turns to water.(也可用will turn)如果把冰加熱,它就會化成水.
5．if從句用現(xiàn)在進行時,主句用一般將來時
If you are looking for Peter you’ll find him upstairs.如果你是在找彼得,上樓就會找到他.
6．if從句用現(xiàn)在完成時,主句用一般將來時
If you have finished dinner I’ll ask the waiter for the bill.如果你吃完了,我就叫服務(wù)生來算賬