1、essential

绝对必要的;必不可少的;基本的

It was absolutely essential to separate crops from the areas that animals used as pasture.

将庄稼和放牧区分开绝对必要。

As they must also sprint over short distances, speed is essential.

由于他们也必须进行短跑，因此速度至关重要。

基本的;本质的；根本的

Most authorities agree that play is an essential part of a child's development.

大多数权威人士都同意，玩耍在孩子成长过程中起着非常重要的作用。

In this trial two essential elements must be proven: motive and opportunity.

在这次审讯中，必须证明两个基本因素：动机和时机。

复数名词（某学科的）基础，基本知识

the essentials of everyday life, such as eating and exercise.

饮食、锻炼等日常生活的要素

This has stripped the contest down to its essentials.

这就使比赛精简到最基本的环节。

2、connection

关系;联系

There was no evidence of a connection between BSE and the brain diseases recently confirmed in cats.

没有证据表明疯牛病与最近确诊的猫类脑病有关联。

The police say he had no connection with the security forces.

警方说他与安全部队没有关系。

关于;与…有关

I am writing in connection with Michael Shower's letter.

关于迈克尔·肖尔的来信，现复信如下。

13 men have been questioned in connection with the murder.

有13名男子因谋杀案受到盘问。