The If Clauses

If Clause Type I

if + Simple Present, will-Future

Type I indicates what will happen, provided that a certain situation is given.

( PRESENT SITUATION, FUTURE CONSEQUENCE )

Examples:

If you send your order by fax, we will deliver the goods immediately.
If you invite me for lunch, I will help you with your presentation.

If Clause Type II

if + Simple Past, would + infinitive

Type II indicates what could happen if a present situation were different.

( IMAGINARY SITUATIONS )

Examples:

If we had more employees, we would work more efficiently.
If we delivered poor quality, we would not be the leading company in our business.

If Clause Type III

if + Past Perfect, would + have + past participle

Type III indicates what could have happened in the past if a situation had been different then.

( REGRETS )

Examples:

If you had read the paper, you would have seen the advertisement.
If I had taken the bus, I would have been late.

#FormATION	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.