Conditional sentences

Conditional sentences - type I

Conditional sentences (if-clauses, main clauses)

Use

It is possible to fulfil a condition which is given in the if-clause.

Form

If Clause	Main Clause
Simple Present	will-future or infinitive or Modal + infinitive

Examples

If I study,	I will pass the exams.
If you see John tonight,	tell him to e-mail me.
If Ben gets up early,	he can catch the bus.

The if-clause can be at the beginning or at the end of the sentence.

If I study,	I will pass the exams.
I will pass the exams	if I study.

Conditional sentences - type II

Conditional sentences (if-clauses, main clauses)

Use

It is theoretically possible to fulfil a condition which is given in the if-clause.

Form

If Clause	Main Clause
Simple Past	would + infinitive or could + infinitive or might + infinitive

Examples

If I studied,	I would pass the exams.
If I studied,	I could pass the exams.
If I studied,	I might pass the exams.

The if-clause can be at the beginning or at the end of the sentence.

If I studied,	I would pass the exams.
I would pass the exams	if I studied.

Conditional sentences - type III

Conditional sentences (if-clauses, main clauses)

Use

It is impossible to fulfil a condition which is given in the if-clause.

Form

If Clause	Main Clause
Past Perfect	would + have + past participle or could + have + past participle or might + have + past participle

Examples

If I had studied,	I would have passed the exams.
If I had studied,	I could have passed the exams.
If I had studied,	I might have passed the exams.

The if-clause can be at the beginning or at the end of the sentence.

If I had studied,	I would have passed the exams
I would have passed the exams	If I had studied,

Conditional sentences - Special types and structures

Conditional sentences (if-clauses, main clauses)

Structure

If-clauses can be clause-initial (1), clause-medial (2) as well as clause-final (3).

(1)	If you like, we can catch a movie.
(2)	We, if you like, can catch a movie.
(3)	We can catch a movie if you like.

Types

Aside from the typical type I, II, III strucure, conditionals can be divided into two categories:
real and unreal conditionals.

Real Condition

If I have money, I spend it.	Present Real Conditional - type I
If I had money, I spent it.	Past Real Conditional - type I
If I have money, I will/am going to spend it.	Future Real Conditional - type I

Unreal Condition

If I had had money, I would have spent it.		Past unreal Conditional - type III
If I had money, I would spend it.	I think about spending the money TODAY.	Present unreal Conditional - type II
If I had money, I would spend it.	I think about spending the money NEXT WEEK.	Future unreal Conditional - type II

Special Features

Modal verbs
Main clauses with real conditional tenses can have modal verbs.

If I have money, I can spend it.

You can use could and might instead of would in unreal conditional clauses.

If I had money, I could spend it. (I would be able to spend it.)

If I had money, I might spend it. (I would possibly spend it.)

Mixed Conditionals

Conditional sentences (if-clauses, main clauses)

Mixed Conditionals

Unreal conditionals (type II + III) sometimes can be mixed, that is, the time of the if clause is different from the one of the main clause.

Past --> Present
If I had taken an aspirin, I wouldn't have a headache now.

Past --> Future
If I had known that you are going to come by tomorrow, I would be in then.

Present --> Past
If she had enough money, she could have done this trip to Hawaii.

Present --> Future
If I were you, I would be spending my vacation in Seattle.

Future --> Past
If I weren't flying to Detroit, I would have planned a trip to Vancouver.

Future --> Present
If I were taking this exam next week, I would be high-strung.