Conditional Sentences

Conditional Sentences are also known as Conditional Clauses or If Clauses. Conditional sentences are made up of two parts: the if-clause (condition) and the main clause.
1. If clause (clause): the sentence can not stand alone / must be attached to the main clause.
There are three types of Conditional Sentences: Future Real Condition, Present Unreal Condition, Past Unreal Condition.
2. Main Clause (Parent sentence): the sentence can stand alone because it has a subject and predicate.

Type I Condition : Future – Real Condition

An action in the future will only happen if a certain condition is fulfilled by that time. We don't know for sure whether the condition actually will be fulfilled or not, but the conditions seems rather realistic, so we think it is likely to happen.

Example 1 : If we arrive late, he will be angry with us.
Fact : possibility he won’t be angry, when we arrive on time
Example 2 : He will not go to the picnic if it rains.
Fact : its no rain, so he going for a picnic

Tense : if + simple present, simple future
Formula : if + S + V1 + will + V1
Or
S + will + if + S + V1 + s/es



Type II Condition : Present – Unreal Condition

An action could happen if the present situation were different. I don't really expect the situation to change, however. I just imagine „what would happen if …“

Example 1 : If I were rich, I would give my money to the poor.
Fact : I’m not rich

Example 2 : If he smokes less, he wouldn’t cough so much.
Fact : he is smoke

Tense : if + simple past, past future tense
Formula : if + V2, S + Would + V1

In this type of conditional, using word “if” can be replaced by using inversion pattern. Inversion is a imaginal form which not using word “if”, as example are following :

- Were he here, he would take care of our problem.
Fact : he isn’t here
- Were I movie star, I would be very famous
Fact : I’m not a movie star

Type III Condition : Past – Unreal Condition

An action could have happened in the past if a certain condition had been fulfilled. Things were different then, however. We just imagine, what would have happened if the situation had been fulfilled.


Example 1 : If I had known her number, I would have called her.
Fact : I didn’t know her
Example 2 : He could have repaired the engine, if he had more tools.
Fact : He didn’t have enough tools

Tense : if + Past Perfect Tense, Past Future Perfect Tense
Formula : if + S + had + V3, S + would have + V3
Or
S + could have + V3, if + S + had + V3

In this type of conditional, we can use inversion pattern by no using word “if’. As example are following :

- Had I gone to the movie, I would have met her.
Fact : I didn’t go to the movie

Formula : Had + S + V3 + Subject + Would Have + V3


References :
http://isakayoga04.blogspot.com/2012/02/conditional-sentences-and-passive-voice.html
http://www.ego4u.com/en/cram-up/grammar/conditional-sentences