CONDITIONALS

Zero Conditional	First Conditional
If + Present Simple, Present Simple General truths e.g. If/Whenever ice melts, it becomes water. Rules e.g. If you wave a red flag, it means danger.	If + Present Simple, will/can + infinitive e.g. If I win the lottery, I will travel around the world. Unless I win the lottery, I will not/ won’t travel around the world. (I don't know if I win but there is a possibility)
Second Conditional	Third Conditional
If + Past Simple, would/could + infinitive e.g. If I won the lottery, I would travel around the world. (But I didn't win the lottery, and it’s very unlikely that I will win)	If + Past Perfect, would/could + have + PP e.g. If Christopher Columbus hadn’t discovered America, the history of the world would have been  different.  (But he had discovered America and it’s impossible to change)

 

Zero Conditional	First Conditional
If + Present Simple, Present Simple e.g. If I have time, I study English. (I sometimes have time)	If + Present Simple, will/can + infinitive e.g. If I have time, I will study English. (I don't know if I will have time or not)
Second Conditional	Third Conditional
If + Past Simple, would/could + infinitive e.g. If I had time, I would study English. (I don't have time)	If + Past Perfect, would/could + have + PP e.g. If I had had time, I would have studied English.   (I didn't have time)