very important or necessary

至关重要的; 必不可少的; 关键的:

China's support is key to the success of the coalition.

中国的支持是联盟成功的关健。

The President makes all the key decisions on foreign policy.

外交政策上所有重要的决定都是总统作出的。

The show has been hit by the departure of key personnel.

由于主要演员离去，演出受到了影响。

LOCK 锁, a small specially shaped piece of metal that you put into a lock and turn in order to lock or unlock a door, start a car etc

钥匙:

I lost my house keys.

我把家里的钥匙弄丢了。

A bunch of keys hung from his belt.

他的腰带上挂着一串钥匙。

I can lend you a spare key to the store until you get one cut (=made).

在你配好钥匙之前，我可以借给你一把店里的备用钥匙。

IMPORTANT PART 重要的部分, the key the part of a plan, action etc, that will make it possible for it to succeed

关键:

Working well as a team is the key to success .

团队合作良好是成功的关键。

a discovery that may hold the key to our understanding of the universe

可能对我们了解宇宙很关键的发现

COMPUTER 计算机, the buttons that you press on a computer KEYBOARD to operate the computer

〔计算机键盘上的〕键:

Press the ESCAPE key to exit.

按 ESCAPE（退出）键退出。

MUSIC 音乐

MAP / DRAWING 地图/图, a list of the signs, colours etc used on a map or technical drawing etc that explains what they mean

图例，符号说明

TEST 测试, the printed answers to a test or set of questions in a book

答案，题解

ISLAND 岛, [usually plural] a small flat island, especially one that is part of a group near the coast

〔尤指靠近海岸的〕小岛，低岛:

the Florida Keys

佛罗里达群岛

[AmE informal] if you key a win for your team, you help it win a game because you play very well

成为〔获胜〕的关键:

Abdul keyed the game with three touch-downs.

阿布杜尔三次持球触地得分，为赢得比赛起了决定性作用。

[BrE] to prepare a surface so that a covering such as paint will stick to it

〔为涂油漆等〕将…的表面处理好