if引导条件状语从句,意为“如果”
If it rains tomorrow,we will stay at home.如果明天下雨,我们就呆在家里.
if引导虚拟条件句,也意为“如果”,此时要注意虚拟条件句的时态.
If I were you,I would do better.如果我是你,我会做的更好.
if引导并宾语从句,意为“是否”
Please tell me if he will come tomorrow.请告诉我他明天是否回来.