Conditional Sentence

In grammar, conditional sentences are sentences discussing factual implications or hypothetical situations and their consequences. Languages use a variety of conditional constructions and verb forms (such as the conditional mood) to form such sentences.

Full conditional sentences contain two clauses: the condition or protasis, and the consequence or apodosis.

If it rains [condition], (then) the picnic will be cancelled [consequence].

Syntactically, the condition is the subordinate clause, and the consequence is the main clause. However, the properties of the entire sentence are primarily determined by the properties of the protasis (condition) (its tense and degree of factualness). There are 3 type in conditional sentences :

Conditional Sentence Type 1

→ It is possible and also very likely that the condition will be fulfilled.

Form: if + Simple Present, will-Future

Example: If I find her address, I’ll send her an invitation.

Conditional Sentence Type 2

→ It is possible but very unlikely, that the condition will be fulfilled.

Form: if + Simple Past, Conditional I (= would + Infinitive)

Example: If I found her address, I would send her an invitation.

Conditional Sentence Type 3

→ It is impossible that the condition will be fulfilled because it refers to the past.

Form: if + Past Perfect, Conditional II (= would + have + Past Participle)

Example: If I had found her address, I would have sent her an invitation.

Example :

1. If I find her address, I will send her an invitation.
2. If I hadn't helped you, you would have failed.
3. If it had been sunny, we could have gone out.
4. If I were you, I wouldn't do that.
5. If I had more time, I would do more on my websites.
6. If I have time today, I will phone my friend.
7. If I go to England, I will buy some Cheddar cheese.
8. If he said that to me, I would run away.
9. If you had called me, I would have come.
10. If you had done your job properly, we wouldn't be in this mess now.

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http://en.wikipedia.org/wiki/Conditional_sentence