Conditionals use “if clauses” and describe the results of possible situations. Conditionals can be tricky because the verb tenses in the conditional clause don’t always refer to the same time period that they usually do. There are four main types of conditionals:
Zero Conditional or “Present Real Conditional”
This conditional talks about the outcome of a real-life condition that is general or often repeated.
| Conditional Clause | Main Clause |
| If + Present Tense | Present Tense |
| If I have a headache, | I lie down. |
| If water is heated to 100° C, | it boils. |
| If you have a new baby, | you don’t get much sleep. |
The “Zero Conditional” is the only conditional in which you can substitute “when” for “if” and have the same meaning.
- When I have a headache, I lie down. = If I have a headache, I lie down.
For this and all conditionals, it doesn’t matter if the conditional clause or main clause comes first. If the conditional clause is first, separate it with a comma.
- If water is heated to 100° C, it boils. = Water boils if it is heated to 100° C.
First Conditional or “Future Real Conditional”
This conditional talks about real future possibilities based on future conditions. Although the present tense is used in the conditional tense, it refers to the future.
| Conditional Clause | Main Clause |
| If + Present Tense | Will + base verb |
| If he asks me to marry him, | I will say “yes.” |
| If this rain keeps up, | we won’t be able to go to the park. |
| If you wash the dishes, | I will dry them. |
You can also use “when” in this conditional, but it changes the meaning. “When” means that the condition is certain to happen; “if” means that it is uncertain.
- “When I go to college, I will major in Physics.” (I am certainly going to college.)
- “If I go to college, I will major in Physics.” (I don’t know if I will go to college or not.)
Second Conditional or “Present Unreal Conditional”
This conditional talks about possibilities that are imagined or impossible. Although the past tense is used in the conditional clause, we are actually talking about the present.
| Conditional Clause | Main Clause |
| If + Simple Past Tense | Would + base verb |
| If I were a marine biologist, | I would go to the bottom of the ocean. |
| If I spoke Spanish, | I would move to Costa Rica. |
| If he were smarter, | he wouldn’t smoke cigarettes. |
| If I knew his email address, | I would write to him. |
Note that although “I was” “she was” and “it was” are the correct forms in the simple past tense, in conditional clauses, the correct conjugations are “I were” “she were” and “it were.”
Third Conditional or “Past Unreal Conditional”
This conditional is used to talk about imagined past situations and what might have happened had they been true.
| Conditional Clause | Main Clause |
| If + Past Perfect Tense | Would have + past participle |
| If I had been more careful, | I wouldn’t have gotten mugged. |
| If we had gone on vacation, | we would have missed your graduation. |
| If I had taken that job in Florida, | I would have been rich. |
Note: Modal Verbs
The examples above are the standard forms of the conditionals, with “will” or “would,” but you can also use other modal verbs, like “can,” “could,” “might,” “may,” or “should.”
- If you don’t like your major, you should change it.
- If I had had more time yesterday, I might have gone to the museum.
- If you don’t wear a helmet when you bike, you can get seriously injured.
- If Jeremy weren’t so busy, he could own a dog.
Mixed Conditionals
There are also “mixed conditionals,” in which the time in the condition doesn’t match the time in the result.
- If I had studied harder in school (past), I would be a doctor now (present).
- If Tom hadn’t gotten expelled (past), he would be graduating with us tomorrow (future).
- If Elizabeth behaved better (present), she could go on the class trip next week (future).
- If you knew calculus (present), you would have helped me with my homework yesterday (past.)
General Tense Rules:
- To talk about the present with “if” = use the past tense
- To talk about the past with “if” = use the past perfect tense