Conditional sentences are sometimes confusing for learners of English as a second language.
There are three types of conditional sentences.
| type | condition |
|---|---|
| I | condition possible to fulfill |
| II | condition in theory possible to fulfill |
| III | condition not possible to fulfill (too late) |
| type | if-clause | main clause |
|---|---|---|
| I | Simple Present | will-future or (Modal + infinitive) |
| II | Simple Past | would + infinitive * |
| III | Past Perfect | would + have + past participle * |
| type | if clause | main clause |
|---|---|---|
| I | If I study , | I will pass the exam. |
| II | If I studied , | I would pass the exam. |
| III | If I had studied , | I would have passed the exam. |
Mind the comma after the if clause.
| type | main clause | if-clause |
|---|---|---|
| I | I will pass the exam | if I study . |
| II | I would pass the exam | if I studied . |
| III | I would have passed the exam | if I had studied . |
| type | Examples | ||
|---|---|---|---|
| long forms | short/contracted forms | ||
| I | + | If I study , I will pass the exam. | If I study , I 'll pass the exam. |
| - | If I study , I will not fail the exam. If I do not study , I will fail the exam. | If I study , I won't fail the exam. If I don't study , I 'll fail the exam. | |
| II | + | If I studied , I would pass the exam. | If I studied , I 'd pass the exam. |
| - | If I studied , I would not fail the exam. If I did not study , I would fail the exam. | If I studied , I wouldn't fail the exam. If I didn't study , I 'd fail the exam. | |
| III | + | If I had studied , I would have passed the exam. | If I 'd studied , I 'd have passed the exam. |
| - | If I had studied , I would not have failed the exam. If I had not studied , I would have failed the exam. | If I 'd studied , I wouldn't have failed the exam. If I hadn't studied , I 'd have failed the exam. | |
* We can substitute could or might for would ( should , may or must are sometimes possible, too).