"if" 是一个条件连词，用于引导条件状语从句或宾语从句。根据不同的语境和时态，"if" 后面的从句可以采用不同的时态。以下是一些常见的 "if" 时态用法：

一般现在时

条件状语从句：当主句是一般将来时时，if 引导的从句通常用一般现在时表示将来的动作或状态。例如：

If it doesn't rain tomorrow, I will go to the zoo.

宾语从句：if 可以引导宾语从句，从句的时态根据具体语境决定。例如：

I don't know if he will visit his grandparents.

一般过去时

条件状语从句：当主句是过去时时，if 引导的从句通常用一般过去时表示过去的动作或状态。例如：

If I had finished my homework yesterday, I could go out and play with you today.

一般将来时

宾语从句：if 可以引导宾语从句，从句的时态根据具体语境决定。例如：

I will go to the movies if I have time.

现在进行时

条件状语从句：在某些情况下，if 引导的从句可以用现在进行时表示将来。例如：

If she is coming to the party, I will prepare the snacks.

过去将来时

宾语从句：if 可以引导宾语从句，从句的时态根据具体语境决定。例如：

He said that he would have another try if he had the chance.

虚拟语气

条件状语从句：在虚拟语气中，if 引导的条件状语从句通常用过去时（simple past tense）表示与现在或将来事实相反的情况，而主句则用过去将来时（would + base form）。例如：

If I were you, I would travel around the world.

一般现在时：

If it rains tomorrow, we will stay at home.

If she is late, she will call me.

一般过去时：

If I had studied harder, I would have passed the exam.

If they had arrived earlier, they would have seen John.

一般将来时：

If you hurry, you will catch the bus.

If he has time, he will help us.

现在进行时：

If she is cooking dinner, the house will be full of delicious smells.

If they are playing football, they will be tired.

过去将来时：

If I knew the answer, I would tell you.

If she had known you were in town, she would have called you.

虚拟语气：

If I were rich, I would travel the world.

If I had more time, I would learn to play the guitar.

希望这些例句能帮助你更好地理解 "if" 的不同时态用法。