Conditional sentences
The conditional sentences are sometimes confusing for learners of English.
Watch out:
1) Which type of the conditional sentences is used?
2) Where is the if-clause (e.g. at the beginning or at the end of the conditional sentence)?
There are three types of the if-clauses.
type
condition
I
condition possible to fulfill
II
condition in theory possible to fulfill
III
condition not possible to fulfill (too late)
Form
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 *
Examples (if-clause at the beginning)
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.
Examples (if-clause at the end)
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.
Examples (affirmative and negative sentences)
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).
I would pass the exam.
I could pass the exam.
I might pass the exam.
I may pass the exam.
I should pass the exam.
I must pass the exam.