necessary名词

名词形式是necessity，表示必需品的意思，例如：

1.There had never been any necessity for her to go out to work.她从来就没有出去工作的必要。

2.This is, of necessity, a brief and incomplete account.这必然是一份简略的、不完全的描述。

3.We recognize the necessity for a written agreement.我们认为有必要签订一份书面协议。