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Conditionals are sentences in which the main-clause as well as the subordinate-clause  express conditions. In each of the clauses one event follows the other or depends upon the other.

Let us look at these sentences

If it rains, I shall stay at home.                                   (1^st Conditional)

I shall stay at home if it rains.

If it rained, I would stay at home.                            (2^nd  Conditional)

I would stay at home if it rained.

If it had rained, I would have stayed at home.     (3^rd  Conditional)

I would have stayed at home if it had rained.

We notice that in each of these sentences have two clauses – the main clause and the subordinate clause.

I will stay at home                                                if it rains.    

Main clause                                                           subordinate clause

We also notice that the subordinate clause begins with if – indicating that the main clause  depends on the condition expressed in the subordinate clause.

We can see that the order of the clauses are interchangeable. We use a comma after the subordinate clause when the sentence begins with ‘If’.

THERE ARE BASICALLY THREE TYPES OF CONDITIONALS

The first conditional – THE PROBABLE OR LIKELY CONDITIONAL

The second conditional -THE ‘HYPOTHETICAL OR UNLIKELY CONDITIONAL

The third conditional -THE IMPOSSIBLE CONDITIONAL

THE FIRST CONDITIONAL

1.THE PROBABLE OR LIKELY CONDITIONAL

The first conditional is used to refer to events or results that are likely to happen if certain condition exists.

If it rains, I will stay at home.

If it doesn’t rain, we shall go for a walk.

Basic form of 1^st conditional

Form	If + present tense  + future

If you see a falling star, your wish will come true.

If he is free, he will give us a call.

If she works hard, she will be successful.

Other forms of likely conditional

If you are tired, take some rest.

Form – If + present tense + imperative.

If mother agrees, we are going for a picnic.

Form – If + present tense + present continuous tense.

If she has prepared the document, I will send it for approval.

Form – If + present perfect tense + future tense.

If she is unwell, she must see a doctor.

Form – If + present  tense +  must/ may/ might / should / can

If they are waiting for the minister, they will be disappointed.

Structure – If + present continuous tense + future tense.

THE SECOND CONDITIONAL

2.  THE ‘HYPOTHETICAL’ OR ‘UNREAL’ CONDITIONALS

These are imaginary situations  in which one wishes that certain things would happen if the conditions existed.

If she studied hard, she would pass.

 If he requested me, I could help her.

If  I were the Environment minister, I would stop all deforestation.

If I were hardworking, I would succeed.

Basic form of 2^nd Conditional. (Unreal)

(If + past tense) +( would [could/ might] + bare infinitive )

If you worked hard, you would succeed. (certain)

If you worked hard, you might succeed. (possibility)

If you worked hard, you could succeed. (ability)

Sometimes we use were to make the sentence polite, or in hope that things would transpire according to our wish. We may omit ‘If’ and start the sentence with ‘were’.

If the global were to rise at a higher rate, we would all perish.

Were he sincere, he would get a promotion.

Were I a millionaire, I would be globe-trotting now.

                                           (continuous tense)

THE THIRD CONDITIONAL

3.THE IMPOSSIBLE CONDITIONAL

The impossible conditional is used to refer to actions that took place in the past and cannot be changed.

If it had rained,I would have got wet.

If he had read the instructions, he would not have broken the gadget.

If they had eaten the stale food, they would have got sick.

If he had climbed the ladder carefully, he would not have slipped.

Basic form of 3^rd conditional

(If + past perfect) + (would [might/ could] + have + past participle)

If he had come on time, he wouldn’t have missed the bus.

If Harry had seen the weather forecast, he wouldn’t have gone out.

Had + subject + past participle

This form can be used to write sentences without using ‘If’.

Had I received the invitation, I would have attended his marriage.

4. ZERO CONDITIONALS.

Zero conditionals are used when we are stating scientific truths or things that are generally true.

If you heat ice, it melts.

Ice melts if you heat it.

If you heat water to 100°C it boils.

Water boils when (if) you heat it at 100°C.

Basic form of zero conditionals

(If + present tense)  + (..present tense)

When it rains, we wear a raincoat.

5. CONDITIONALS WITHOUT ‘IF’

Conditional sentences without ‘if’ use words like ‘as long as’, ‘ unless’, otherwise, ‘provided that’, ‘providing’, ‘or’ , ‘otherwise’.

Unless he hurries, he will miss the train.

She can borrow my books as long as she returns them on time.

You must complete your homework, otherwise you will be punished.

We shall go for a picnic, provided that the weather is fine.