This is the 244th most frequent Chinese word.
关键
Key; crucial; critical.
The word '关键' here refers to the critical or pivotal point needed to address or tackle an issue.
找到问题的关键是解决问题的第一步。
Finding the key to the problem is the first step to resolving it.
In this sentence, '关键' is used to describe something essential or indispensable for achieving a function.
这个按钮是操作机器的关键。
This button is crucial for operating the machine.
Here, '关键' indicates a primary or determining factor that contributes to the outcome of a process or goal.