If

First Conditional

If clause                                    Main clause

If + Present Simple                       will

The present tense refers to a possible future action, something which may or may not happen.

• If I have money, I will buy a car.
• If we hurry, we will catch the bus.
• If it rains, we will stay at home.

 The main clause often has will. But we can use other modal verbs.

• If he helps me, I may finish the project on time.
• If you don’t feel well, you must go to the doctor.

We can use First Conditionals in offers and suggestions. We can also use them in warnings and threats.

• If you don’t come to my birthday party, I’ll never speak to you again.
• If you say that again, I will hurt you!
• If you try very hard, you'll see the difference.
• John will be late, if you don't lend him your car.

Second Conditional

If clause                                 main clause

If + Past Simple                          would

The past tense refers to something unreal. If I had a million dollars means that I haven’t really got a million dollars, but I am imagining that I have.

• If I won a million dollars, I would travel around the world. (There is a small possibility that I would actually win.)
• If things were different, we would be happy. (In reality things are not different, and we are not happy.)
• If I had his number, I would call him. (I don't have his number now, so it's impossible for me to call him).
• If I had money, I would buy a car.
• If I lived in New York, I would go to the Central Park.
• If she didn’t like her job, she would change it.

In If Clauses Type II, we usually use ‚were even if the pronoun is I, he, she or it. Note the form 'If I were you' which is often used to give advice.

• If I were you I would apologize. (In reality I am not you.)
• If she were an honest person, I would believe in her.
• If we were rich, we would live in Paris.
• If I knew her name, I would tell you.
• If I were you, I'd look for a new place to live.