essential与vital用法有什么区别？

要想理解这两个词的细微区别，得先从vital开始。

• The heart is a vital organ.

• A patient's vital signs are their important body functions, such as pulse rate, that show they are still alive.

• If you are vital to the organization you work for, it means they can't live without you -- or at least that you're an important part of the team.

从以上例句可见，vital的东西，是缺少了之后可能会致命的（包括抽象的致命）；而essential则强调最基本的（basic and fundamental），例句如下：

• Water is essential for life.   对于生命来说，水是最基本的

• Even in small companies, computers are an essential tool.

• She packed a few essentials.     最基本的生活必须品（名词）

• We have no reason to doubt the essentials of the girl's story.    对这个故事的基本面或大体框架没有怀疑。
  

虽然他们都有重要的意思。但是essential强调基本的，基础的。vital强调重要性。