I + was or were?

Trong ngữ pháp English, tobe thường chia các ngôi của chủ ngữ (S) đi cùng nó. 
Tuy nhiên, có khi nào các bạn tự hỏi, tại sao I lúc thì đi với Was, lúc lại đi với Were?


Câu trả lời là:

In past simple: 

I + Was....
Eg: I was born in 1989. My sister was born in 1991. But you were born in 2000, didn't you remember?

Type 3 Conditional:

If I + Were...
Eg: If I were you, I would never meet him again.




Reference: http://grammar.ccc.commnet.edu/grammar/to_be.htm