necessity是什么意思

　　This is, of necessity, a brief and incomplete account.

　　這必然是一份簡略的、不完全的描述。

　　We recognize the necessity for a written agreement.

　　我們認為有必要簽訂一份書面協議。

　　We were discussing the necessity of employing more staff.

　　我們在討論是否需要雇用更多員工。

　　Air-conditioning is an absolute necessity in this climate.

　　這樣的氣候絕對需要有空調。

　　Water is a basic necessity of life.

　　生命離不開水。