or和either的用法區別

　　Do you want one or two?

　　你要一個還是兩個？

　　The operation could prolong his life by two or three years.

　　這次手術可使他多活兩三年。

　　Well, I think she's either Russian or Polish.

　　嗯，我看她不是俄羅斯人就是波蘭人。

　　There is a large window on either side of the front door.

　　前門兩側各有一個大窗戶。