Conditional Sentence

WHAT IS CONDITIONAL SENTENCE?

Conditional sentences are statements discussing known factors or hypothetical situations and their consequences. These sentences use conditional construction and verb forms, which is called the conditional mood. Complete conditional sentences contain a conditional clause and the consequence.
Languages use a variety of grammatical forms and constructions in conditional sentences. The forms of verbs used in the protasis and apodosis are often subject to particular rules as regards their tense and mood. Many languages have a specialized type of verb form called the conditional mood – broadly equivalent in meaning to the English "would (do something)" – for use in some types of conditional sentence.
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 three types of Conditional Sentences.

THE ZERO CONDITIONAL

The zero conditional is used for when the time being referred to is now or always and the situation is real and possible. The zero conditional is often used to refer to general truths. The tense in both parts of the sentence is the simple present. In zero conditional sentences, the word "if" can usually be replaced by the word "when" without changing the meaning. 

Form:

If + Simple Present, + Simple Present

Examples:

• If you play with a knife, you cut yourself. 

The act of cutting yourself only happens on the condition of the first clause being completed. However such sentences can be formulated with a variety of tenses (and moods), as appropriate to the situation.

• If I you don't drink for a long time, you become thristy.

 This form of the conditional expresses the idea that a universally known fact is being described

IF CONDITIONAL TYPE 1

The type 1 conditional refers to a possible condition and its probable result. These sentences are based on facts, and they are used to make statements about the real world, and about particular situations. We often use such sentences to give warnings. In type 1 conditional sentences, the time is the present or future and the situation is real. These situations take place if a certain condition is met. It is possible and also very likely that the condition will be fulfilled.

Form:

If + Simple Present, + Simple Future

Examples:

• If I am hungry, I will get something to eat.

• If you are hungry, you can eat an apple.

• If it rains, we may get wet.

Exercise

1. If she ……………….. (invite) me, I ………………. (go)
2. If it ……………………. (rain), we …………………… (cancel) the match.
3. If I ……………….. (get) a promotion, I ………………… (buy) a car.
4. If she ………………. (be late), we …………………. (go) without her.
5. If you ………………. (ask) more politely, I ………………… (buy) you a drink.

Answers

1. If she invites me, I will go.
2. If it rains, we will cancel the match.
3. If I get a promotion, I will buy a car.
4. If she is late, we will go without her.
5. If you ask more politely, I will buy you a drink.

In all of these examples, the second event is only true where the first event or condition is completed.

IF CONDITIONAL TYPE 2

The type 2 conditional is used to refer to a time that is now or any time, and a situation that is unreal. These sentences are not based on fact. The type 2 conditional is used to refer to a hypothetical condition and its probable result. In type 2 conditional sentences, the if clause uses the simple past, and the main clause uses the present conditional.

Form:

if + Simple Past, + would + infinitive

Were / Was

In conditional type 2, we usually use in the if clause "were" instead of "was" even if the pronoun is I, he, she or it. "were" here is a subjunctive form.

NOTE: "was" is also a possible form.

Examples:

• If she fell, she would hurt herself.
• If you really loved me, you would buy me a diamond ring.
• He could go to the concert if you gave him your ticket.

All of the above examples are technically possible situations (it’s possible to go to the concert, if you give him your ticket) but they are all very unlikely situations. To express this, we use the second conditional tense.

Exercise

1. If I _________ (play) the lottery, I __________ (have) a chance to hit the jackpot.
2. If I _______ (hit) the jackpot, I _________ (be) rich.
3. If I _________ (be) rich, my life _______ (change) completely.
4. I _________ (buy) a lonely island if I ________ (find) a nice one.
5. If I _____ (own) a lonely island, I ________ (build) a huge house by the beach.

Answers

1. If I played the lottery, I would have a chance to hit the jackpot.
2. If I hit the jackpot, I would be rich.
3. If I were rich, my life would change completely.
4. I would buy a lonely island if I found a nice one.
5. If I owned a lonely island, I would build a huge house by the beach.

IF CONDITIONAL TYPE 3

The type 3 conditional is used to refer to a time that is in the past, and a situation that is contrary to reality. The facts they are based on are the opposite of what is expressed. The type 3 conditional is used to refer to an unreal past condition and its probable past result. In type 3 conditional sentences, the if clause uses the past perfect, and the main clause uses the perfect conditional.

Form:

if + Past Perfect, + would + have + Past Participle

Examples:

• If you had swallowed some of the cleaning fluid, it would have killed you.
• If I had had a little humility, I would have been perfect.
• If you had warned me, I would not have told your father about that party.

Using " unless"

"Unless" means the same as "if ... not", and has a negative value. It is frequently (but not only) used in conditional statements where the verb of the main clause is also  in the negative.

  Examples:

• Our marketing director would not have signed the contract unless she'd had the company legal expert present.
• I wouldn't have phoned him unless you'd suggested it.
• They would have shot her unless she'd given them the money.

Exercise 

1. If the midfielders ______ (pass) the ball more exactly, our team ____ (have) more chances to attack.
2. If the forwards ___________ (have/run) faster, they _____________ (score) more goals.
3. Their motivation ________ (have/improve) if they _________ (have/kick)a goal during the first half.
4. The fullbacks _____ (have/prevent) one or the other goal if they ____ (have/mark) their opponents.
5. If the goalie _____________(have/jump), he ______________ (have/catch) the ball.

Answers

1. If the midfielders had passed the ball more exactly, our team would have had more chances to attack.
2. If the forwards had run faster, they would have scored more goals.
3. Their motivation would have improved if they had kicked a goal during the first half.
4. The fullbacks would have prevented one or the other goal if they had marked their opponents.
5. If the goalie had jumped up, he would have caught the ball. 

Things to remember

1. The main clause can also be at the beginning of the sentence. In this case, don't use a comma.

Examples: 

• Someone will let you know if you make a mistake.
• I would dance in the street if it were to rain tomorrow. 
• I would attend more of them if I liked parties.

2. Main clause and/or if clause might be negative.

Example:

• If I don’t see him this afternoon, I will phone him in the evening.
• If he had been careful, he wouldn't have had an accident.

References: 
https://en.wikipedia.org/wiki/Conditional_sentence
http://www.englishpedia.net/grammar-exercises/if-clauses/conditionals-type-three-3-lesson-exercises.html

http://istudyenglishonline.com/english-tenses/conditional/

http://www.edufind.com/english-grammar/conditional/

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

https://www.ego4u.com/en/cram-up/grammar/conditional-sentences\

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