CONDITIONAL CLAUSES THEORY

If clause	Main clause	EXAMPLES
If + present	Future Simple Imperative Present Simple (Zero conditional: facts, general truths) Modal (Present):  can, may, must, should + infinitive	If you study, you will pass. If you go to London, bring me a souvenir If you sit on the sun, you get sunburnt  If you try hard, you can get better
If + Past Simple (2)	would+ infinitive Modal Past: could or might + infinitive	If I were you, I would tell her the truth. If I had more money, I could/might buy a car.
If + Past Perfect (3)	would have+ past participle   could or might have+ past participle	If I had known she was ill, I would have visited her. If you had followed a diet, you could/might have lost weight.

VARIATIONS OF THE IF-CLAUSE

1.  IF +Present continuous and present perfect are also possible in 1^st type conditionals

2. IF + Past continuous OR PAST PERFECT  can also be used in 2^nd type conditionals.

If he had taken my advice, he would be a rich man now. (A combination of types 2 and 3 )

3. IF + Past perfect continuous can also be used in 3^rd type conditionals. 

1st. CONDITIONAL is used :

To talk about the future, or about facts or situations which are or can be true in the present and future.

2nd. CONDITIONAL is used:

To express hypothetical or imaginary situations .

3rd. CONDITIONAL is used:

To refer to the past, reason why the actions did not happen and cannot happen any more.

CONDITIONAL LINKERS

If is the most common linker used in conditional clauses, but there are others:

Even if is used to emphasize the conditional clause
In case: por si
Take an umbrella in case it rains.

Unless = If ..not (1^st type conditional)

As long as = Only if ( 1^st type conditional)

Providing / Provided that = Only if ( 1^st type conditional)

On condition that= Only if ( 1^st type conditional)

ALTERNATIVE STRUCTURES

I wish / If only (Ojalá).

I wish + Past Simple or Continuous

When we want something to be different in the present.

I wish + Past Perf.

To express regret for something we did in the past.

I wish + Conditional Simple

To complain about something in the present.

If only is used to show more emphasis than I wish