1
- absolutely necessary; extremely important必不可少的; 绝对必要的; 非常重要的：
with infinitive it is essential to keep up-to-date records随时做好记录是十分必要的
fibre is an essential ingredient of our diet.
纤维素是我们饮食中一种必不可少的成分。
1.1
- attrib. fundamental or central to the nature of something or someone本质的; 基本的; 精髓的, 精华的：
the essential weakness of the plaintiff's case.
原告讼案的根本弱点。
1.2
- (of an amino acid or fatty acid) required for normal growth but not synthesized in the body and therefore necessary in the diet（氨基酸, 脂肪酸）必需的。
2
- Medicine (of a disease) with no known external stimulus or cause; idiopathic【医】（疾病）自发的, 原发的, 特发的：
essential hypertension.
原发性高血压。
(一般作essentials)
1- a thing that is absolutely necessary必不可少的东西; 必需品：
we only had the bare essentials in the way of equipment.
我们只是有了最基本的必需设备。
1.1
essentials
the fundamental elements or characteristics of something要素; 本质, 实质：he was quick to grasp the essentials of an opponent's argument.
他很快抓住了对手论据的要旨。
派生词
essentiality
nounessentialness
noun词源
Middle English （in the sense 'in the highest degree'）： from late Latin essentialis, from Latin essentia （see ESSENCE）.