adj.本质的；必要的；重要的
n.要素；必需品
This is of course still the essential method. 这当然仍是本质的方法。
This is desirable but by no means essential to the primary objective of validating mathematical models of aircraft behaviour. 对于验证飞机性能的数学模型这一主要目的来说，这是必须的，但决不是最本质的.
Concentration is essential if you want to do a good job. 如果你想把事情做好,专心是必要的。
用作名词 (n.)What are the essentials of good teaching? 成功教学的要素是什么?
The first essential, of course, is to know what you want. 第一要素当然是知道自己想要什么。
We only had time to pack a few essentials. 我们只来得及装上几件必需品。
A man should never neglect these social essentials. 一个人决不该疏忽了这些社交上的必需品。
essential用作形容词指事物赖以存在或与他物相区别的“最基本的”东西。一般与to或for连用,表示“对…是要紧的”。
essential用于“It is/was essential+that-clause”结构时, that从句要用虚拟语气。
