necessity
n. 必需品，必需的事物；必要，需要；必然性，不可避免的情况
复数 necessities
例句
Water is a basic necessity of life.
水是一种基本生活必需品。
《柯林斯英汉双解大词典》
There is agreement on the necessity of reforms.
关于改革的必要性有一致意见。
We were discussing the necessity of employing more staff.
我们在讨论是否需要雇用更多员工。
《牛津词典》
