Conditions sentense

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.

Omitting if
Had I known... (instead of If I had known...)
Were you my daughter,... (instead of: If you were my daughter,...)
Should you need my advice,... (instead of: If you should need my advice,...)

if vs. when
if and when are interchangeable when the statement of the conditional clause is a fact or a general issue (also known as zero conditonal)

If you heat ice, it melts.
When you heat ice, it melts.

if is used for something that, according to the speaker, might happen.
We can spend the afternoon on the beach if the weather is fine.
when is used for something that, according to the speaker, will happen.
I will clean up the kitchen right away when I'm back from work.

in case vs. if
in case of can be used to shorten an if-clause as shown below:
If there is a fire, leave the room.
In case of fire, leave the room.
While if expresses a condition (1), in case is used to express a possibility (2).
(1)
I need painkillers if I'm in severe pain.
(2)
I need painkillers in case I'm in severe pain.
The expression just in case is used pretty much the same way.
I got you a pizza just in case you were hungry. (I don't know whether you are hungry.)

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