Conditional Sentences

Conditional Sentences (Conditional Clauses or If Clauses) are sentences that built from two main parts, condition part and consquence part. In other source, the condition part is called as protasis while the consequence part being called as apodosis. 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.

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).

Usually, Conditional sentences are divided into:

• Factual. In these constructions, the condition clause expresses a condition the truth of which is unverified. The verb in the condition clause is in the past tense (with a past tense interpretation) or in the present tense (with a present or future tense interpretation). The result clause can be in the past, present, or future. This type is also called as Real conditional sentence because describing real situation that already happen, can happen or have chance to be happened (not impossible, based on fact). That's why this type is used to describe rules.
• Counterfactual. In these constructions, the condition clause expresses a condition that is known to be false, or presented as unlikely. The result clause contains a conditional verb form consisting of would (or could, should, might) plus a main verb in the base form (infinitive without to). This type is also called as Unreal conditional sentence because describing something imaginary, have no chance to happen or just a what-if situation.

Example:

1. (Present Real Conditional) If I have gun, I shoot someone.
2. (Past Real Conditional) If I had gun, I did shoot someone.
3. (Future Real Conditional) I will shoot someone, if you give me a gun.
4. (Present Unreal Conditional) If I had jacket, I wouldn't be sick.
5. (Past Unreal Conditional) If I had had money, I would have bought a jetplane.
6. (Future Unreal Conditional) If I could get some time, I would clean my room.
7. (Future Real Conditional) If I find a treasure tomorrow, I'll give it to her.
8. (Present Unreal Conditional) If only I had a car, I wouldn't be late.
9. (Past Real Conditional) When I was young, I always bought candy if I had money.
10. (Present Real Conditional) If I do my homework now, I sleep late.

Source [wikipedia] [englishpage]