ess＝to be（存在） 变化型 est
1 [esp pred 尤作表语] ~ (to/for sth) necessary; indispensable; most important 必要; 不可缺少; 最重要
*Is money essential to happiness? 金钱对于幸福是必不可少的吗?
* It's essential that you attend all the meetings. 你务必要参加所有的会议.
* `Secretary wanted
*previous experience essential.' ｀招聘秘书
2 [attrib 作定语] relating to sb's/sth's basic nature; fundamental 本质的; 基本的
*His essential decency makes it impossible to dislike him. 他十分正派, 使人不能不喜欢他.
* What is the essential theme of the play? 这剧本的主题是什么?
n (usu pl 通常作复数) fundamentally necessary element or thing 要素; 要点
*A knowledge of French is an absolute essential. 会些法语是非常必要的.
* the essentials of English grammar 英语语法纲要
* We only had time to pack a few essentials. 我们只来得及装上几件必需品.
1. The first essential in elephant training is to assign to the animal a single mahout who will be entirely responsible for the job. 驯象中至关生要的是指派一名专门的驯象员，全面负责这项工作。
2. Lack of physical and mental energy, both of which are essential in turning out and throwing away, and sentiment. 一是体力，精力均告不佳，这二者是清除无用的东西必不可少的因素；另一原因是感情因素。
3. This is culture shock. Evidently, at least four essential stages of culture-shock adjustment occur. 这就是文化冲击。很明显，在人们适应文化冲击的过程中至少会出现四个主要阶段。
4. They deny the excessive time they're devoting to work, and they rationalize that their schedule is for the family and essential to being promoted. 他们否认自己在工作上花了太多的时间，他们自我辩解地说他们的工作是为了家庭，同时对升职也至关重要。
5. Yet to both classes, the need of an alternative outlook, of a change of atmosphere, of a diversion of effort, is essential. 然而对这两种人来说，都需要换一换脑子，改变一下气氛，转移一下注意力，这是不可缺少的。
6. Providing meaningful and quality input into the virtual classroom is an essential part of online learning. 要花时间斟酌并仔细作答，
7. Preventing the destruction of essential proteins in the diet and allowing them to be absorbed in a state more easily utilized by the skin. 防止食物中的基本蛋白质被破坏，使其能以一种更易为皮肤所用的状态被吸收。
8. More than half of the home computers sold in the United States in recent years will become essential to home life in the West. Future tasks computers already do at home include: 近年来在美国售出的家庭电脑有半数以上将成为西方家庭生活的必需品。电脑已经在家庭中发挥的未来功能有：
9. Computers turn on the lights, heating and essential household services before people arrive home from work. Computers control cooking, hot water, security. 在人们下班回来之前，电脑会打开电灯、暖气和其他基本的家庭设施。做饭、烧热水和安全系统都由电脑控制。
10. Is money essential to happiness? 金钱对於幸福是必不可少的吗?