Type I
Context: At the beginning of the school year a teacher says to a student:

• I know you had problems with English last year, but if you work hard you will pass.
  
  Type II
  Context: After failing the first term:
  
• If you worked hard, you would pass.
  
  Type III
  Context: After failing in June.
  
• If you had worked hard, you would have passed.
  

• if + present simple ... future simple:
  
  • If you take more exercise, you will feel better.
  • If you eat too much sugar, your teeth will rot.

• if + present simple ... present simple:
  • If you visit London, you are bound to see the Big Ben.
  • If you heat ice, it turns to water.

• if + present simple ... imperative:
  • If you feel cold, turn down the air conditioning.
  • If you don't like the vegetables, have some more salad.

• if + present simple ... modal + V:
  • If you see George, you must ask him to dinner some day.
  • If you need help, you can use the dictionary.

• if + present continuous ... imperative or modal + V:
  • If Charles is sleeping, don't wake him up.
  • If you are working, I can come back later.

• if + present perfect ... imperative or modal + V:
  • If you have finished the first exercise, do the second one.
  • If you haven't heard from her, you can e-mail her.

• if + future ... future (it is used when striking a deal to share housework, group work, etc.):
  • I will cook if you will do the washing-up.

• if + simple past ... simple conditional:
  
  • If you gave up smoking, your health would improve.
  • If you were a woman, you would think differently.

• if + simple past ... modal + V:
  • If you worked for the BBC, you could travel around the world.
  • If you studied a bit more, you might pass your exams.

• if + simple past ... perfect conditional / modal + V:
  • If I didn't talk so much in class, I wouldn't have failed the last exam.
  • If my teacher didn't give us so much homework, we could have made plans for the long weekend.
  
  (Notice how we use "were" instead of "was" —this is the subjunctive of the verb BE):
  
  • If he weren't so mean, he might have paid for the drinks.
  • If I were rich, I could have gone to the Caribbean on holidays.

• if + past continuous ... perfect conditional / simple conditional / modal + V :
  • If you weren't always complaining, they would have invited you to go on the trip with them.
  • If I wasn't seeing it with my own eyes, I would not believe it.
  • If you weren't talking so loudly, we might hear what they are saying.

• if + should + V ... conditional:
  • If Harrison Ford should become the president of the United States, my old English teacher would feel very happy.

• if + past perfect ... perfect conditional:
  
  • If you had come with us you would have met Mary's new boyfriend.
  • If you had lived in Europe in the Middle Ages, you wouldn't have known tomatoes.

• if + past perfect ... simple conditional:
  
  • If he had survived the accident he would be fifty years old today.
  • If you had saved some money, you would have enough to buy a new computer now.
  
  
• if + past perfect ... modal + V:
  
  • If you had bought the lettuce, we could make a salad.
  
  
• if + past perfect continuous ... perfect conditional + V:
  
  • If they had been working, their teacher wouldn't have got angry when he came into the classroom.
  
  
• if + past perfect continuous ... perfect modal + V:
  
  • If you hadn't been making so much noise, we might have heard the baby cry.

1. Type I
   When we want to share jobs and the deal depends on another person being willing to do their part, we can use "will" in both sentences:
   
   
   I will look for the information for the project on the Internet if you will write out the presentation. (That means more or less: "Yo haré esto si tú quieres hacer esto otro.")
   
   
   Similarly, "would" can be used to reproach someone who is not willing to do something, or to complain about their lack of cooperation, for example:
   
   
   If you would help more with the household chores, I would have more time to spend with the children. (That means more or less: "Si tú quisieras ayudarme más...")
   
   
2. Type II
   When we want to express a very remote possibility, we use "should + V_inf" instead of the simple past:
   
   
   If Donald Trump should become the best president in the history of the USA, many people would be very surprised.
   
   
3. Type III
   In formal English, the third type of conditional can begin with "had" instead of "if":
   
   
   If I had known you were coming, I would have bought more bread. =
   Had I known you were coming, I would have bought more bread.

I won't help you unless you ask nicely. = I won't help you if you don't ask nicely.

© Juan José Castaño