Unreal Conditional

Sentences in the "unreal" conditional have one part of the sentence that begins with the word "if" and contains a verb in what looks like the past tense (Review past tense) and another part of the sentence which contains the modal verb "would."  The conditional with "would" was taught in Intermediate Lesson 5 (Review conditional). If the part of the sentence with "if" goes first, use a comma.  These sentences are known as "unreal" conditional because they contain conditions that are not likely (probable).  For example, in the sentence below, winning the lottery is not very likely. 

If I won the lottery, I would buy a new car. 
I would buy a new car if I won the lottery.

As I mentioned before, the verb in the part of the sentence beginning with "if" is put in what looks like past tense form.  The only exception is with the verb "to be."  It has traditionally been considered to be grammatically correct to use "were" even with the first person singular ("I") and the third person singular (he/she/it).

If I were rich, I would travel around the world.

Although in the past it was considered bad grammar, now many people use "was" in these cases. You now sometimes even see "was" listed as an alternative in grammar books.

If I was rich, I would travel around the world.