Conditional sentences

Conditional sentences are sometimes confusing for learners of English as a second language.

Watch out:

1. Which type of conditional sentences is it?
2. Where is the if-clause (e.g. at the beginning or at the end of the conditional sentence)?

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)

1. 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 *

2. Examples (if-clause at the beginning)

type	if clause	main clause
I	If Istudy,	I will pass the exam.
II	If Istudied,	I would pass the exam.
III	If I had studied,	I would have passed the exam.

3. Examples (if-clause at the end)

type	main clause	if-clause
I	I will pass the exam	if Istudy.
II	I would pass the exam	if Istudied.
III	I would have passed the exam	if I had studied.

4. Examples (affirmative and negative sentences)

type		Examples
		long forms	short/contracted forms
I	+	If Istudy, Iwill pass the exam.	If I study, I'll passthe exam.
	-	If Istudy, Iwill not fail the exam. If I do not study, Iwill failthe exam.	If I study, I won't fail the exam. If I don't study, I'll fail the exam.
II	+	If Istudied, I would pass the exam.	If I studied, I'd pass the exam.
	-	If Istudied, I would not failthe exam. If I did not study, Iwould fail the exam.	If I studied, Iwouldn't fail the exam. If I didn't study, I'd fail the exam.
III	+	If I had studied, I would have passedthe exam.	If I'd studied, I'd have passed the exam.
	-	If I had studied, I would not have failedthe exam. If I had not studied, I would have failedthe exam.	If I'd studied, Iwouldn't have failed the exam. If I hadn't studied, I'd have failed the exam.

* We can substitute could or might forwould (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.