Conditional Sentences

Hello pupils!

Today we are going to talk about conditional sentences. Conditional sentences are also known as conditional clauses or If-clauses. They are used to express that the action in the main clause (without if) can only take place if a certain condition (in the clause with if) is fulfilled. There are four types of conditional sentences: Zero conditional (Type 0), First conditional (Type I), Second conditional (Type II) and Third conditional (Type III). Traditionally, zero conditionals and first conditionals are grouped together into the First conditional type, but we are going to study them apart.

Zero Conditional
The zero conditional is a structure used for talking about general truths, or scientific facts, that is, things which always happen under certain conditions. Therefore, the condition is called real condition. A zero conditional sentence consists of two clauses, a subordinate clause (or if-clause) and a main clause. Present Simple is the tense used in both clauses: [if + Present Simple] + [Present Simple].

For example:
If you cross an international date line, the time changes.
Phosphorus burns if you expose it to air.
If you don't water plants, they die.

See, when the if-clause comes first, a comma is usually used. If the if-clause comes second, there is no need for a comma. Note that most zero conditional sentences will mean the same thing if when is used instead of if. For example:
Phosphorus burns when you expose it to air.
When you don't water plants, they die.


First Conditional
The first conditional (conveying the so-called open conditions) is a structure used for talking about possibilities in the present or in the future. Present Simple is used in the subordinate clause whereas future with will is used in the main clause: [if + Present Simple] + [will + infinitive].

Examples:
If I have the money, I will buy this car.
If it's sunny, we'll go to the park.
Peter will be sad if Susan leaves.
If you cook dinner, I'll wash the dishes.

Among other variations, can and imperative are also possible instead of will:
If it doesn't rain, we can go to the beach.
If you drink alcohol, don't drive.
You can pass the subject if you resit the exam.
Call me if you arrive late.

Remember that unless is often used instead of if in a negative clause:
You'll get wet in the rain if you don't take an umbrella with you.
You'll get wet in the rain unless you take an umbrella with you.


Second Conditional
The second conditional (also referred to as unreal, hypothetical or theoretical conditions) is a structure used for talking about unreal situations in the present or in the future. Past Simple is used in the subordinate clause and Present Conditional is employed in the main clause:
[if + Past Simple] + [would + infinitive].

Examples:
If I had the money, I would buy this car.
If dogs had wings, they would be able to fly.
Paula would be sad if Jan left.
I'd pass my exams if I studied harder.

When the verb in the subordinate clause is to be, we use a unique form were for all persons. This is characteristic of British English. In American English, however, was and were forms are admitted.
If I were you, I would drive more carefully in the rain.  (AmE: If I was you...)
I would buy an island on the Pacific If I were rich.  (AmE: ... if I was rich.)

Other variations include could or might instead of would:
If I were President Obama I could rule the world.
If it didn't rain we might go to the concert. 


Third Conditional
The third conditional (expressing past hypothetical conditions) is a structure used for talking about unreal situations in the past. In other words, it is used to talk about things which did not happen in the past and therefore they are impossible to carry out now. In the if-clause we use Past Perfect, and in the main clause Perfect Conditional is used: [if + Past Perfect] + [would have + past participle].

Examples:
If I had had the money, I would have bought this Audi.
If you had driven more carefully, you would not have had an accident.
If we had played a little better, we would have won the game.

Other variations include could have and might have instead of would have:
If we had played a little better, we could have won the game.
I might have spoken a perfect English if my grandma had married an Englishman.



Practice:
Exercise1, Exercise2, Exercise3, Exercise4, Exercise5, Exercise6.

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