1) ZERO CONDITIONAL
We zero conditional to express general truths and facts (often things based on scientific fact) and we use with the simple present tense.
Formation
| If + Present Tense, | Present Tense |
| If you heat water to 100ºC, | it boils. |
| Present Tense | if + Present Tense |
| Water boils | if you heat it to 100ºC. |
Example:
- If you drop an apple, it falls. = An apple falls if you drop it. (This is an absolute truth based on scientific fact - gravity).
- If you don't do your homework, I am disappointed. = I am disappointed if you don't do your homework. (This is a general truth based on previous knowledge - you know that I am disappointed if people don't do their homework).
NOTE: Most zero conditional sentences mean the same thing if "when" is used instead of "if".
2) FIRST CONDITIONAL
We use first conditional to express situations based on fact in the present or future (things which may happen) and we use with the simple future tense with “will”.
Formation
| If + Present Tense, | Future “will” |
| If I go there, | I will see our teacher. |
| Future “will” | if + Present Tense |
| I will see our teacher | if I go there. |
NOTE:
- We never use will or won't in the “if clause”.
- We often use unless which means “if ... not”.
Example:
- If I have time today, I will phone my friend. = I will phone my friend if I have time today. (It is possible that I will have time – therefore the condition is real).
- If I go to England, I will buy some Cheddar cheese. = I will buy some Cheddar cheese if I go to England. (It is possible that I will go to England - therefore the condition is real).
3) SECOND CONDITIONAL
We use second conditional to express unreal situations in the present or future. It is often used to express a wish with the simple past tense and “would”.
Formation
| If + Past Simple, | Past Future “would” |
| If I were you, | I would marry her. |
| Past Future “would” | if + Past Simple |
| I would marry her | if I were you. |
NOTE: We never use would or wouldn't in the “if clause”.
Example:
- If I were you, I wouldn't do that. = I wouldn't do that if I were you. (I am not you - therefore the condition is unreal).
- If I had more time, I would do more on my websites. = I would do more on my websites if I had more time. (I don't have more time - therefore the condition is unreal).
4) THIRD CONDITIONAL
We use third conditional to express conditions in the past that did not happen. It is often used to express criticism or regret with would have, could have or should have and we use third conditional with the past perfect tense.
Formation
| If + Past Perfect, | Past Future Perfect |
| If I had met her, | I would have told her about my heart. |
| If I had met her, | I could have told her about my heart. |
| If I had met her, | I should have told her about my heart. |
| Past Future Perfect | if + Past Perfect |
| I would have told her about my heart | if I had met her. |
| I could have told her about my heart | if I had met her. |
| I should have told her about my heart | if I had met her. |
NOTE: We never use would have, or wouldn't have etc in the “if clause”.
Example:
- If I hadn't helped you, you would have failed. = You would have failed if I hadn't helped you. (I helped you so you didn't fail).
- If it had been sunny, we could have gone out. = We could have gone out if it had been sunny. (We didn't go out because it wasn't sunny).
