介绍:
nail 指甲
If you see two of your classmates fighting tooth and nail，you must stop them at once. Otherwise, at least one of them would be hurt.
Nail also means a thin pointed piece of metal for hand hammering into something. But it is related to the body in this sentence：“ Peter is as hard as nails. ” We all hope that we are as strong as healthy as he is.
Then ，if I say you have hit the nail on the head, I do not mean that you have done something cruel. I mean that you have said exactly the right thing.
如果你看到你的同学又抓又咬的打起架来，你就应马上制止他们，否则他们其中至少一人会受伤。
nail的另一个解释是钉子，但在句子Peter is as hard as nails（彼得结实得像铁打似的）中却和身体有关。我们都希望自己同样结实强健。
如果我说：you have hit the nail on the head，并不是说你做了残忍的事，我是指你说的非常中肯，真是一针见血。
