Should置於句首，而省略 if, 意思是「萬一」

文法解說2：should 置於句首，而省略 if, 意思是「萬一」

〈長髮姑娘〉ＣＤ２３ If you will promise that should you ever have a daughter, you’ll give her to me for my own. 　

"Should you ever have a daughter, you'll give her to me for my own." 　
= If you should ever have a daughter, you'll give her to me for my own.

例句１：If anyone should come， say I am not at home. 　　
= Should anyone come， say I am not at home. 萬一有人來訪，就說我不在家。

例句２：If it should rain tomorrow, I wouldn't go.
= Should it rain tomorrow， I wouldn't go. 萬一明天天下雨，我就不去了。