This is the 10129th most frequent Korean word.
관건이다
"To be the key or crucial factor."
In this sentence, '관건이다' emphasizes the importance or critical factor necessary in resolving an issue.
문제 해결의 관건이다.
It is the key to solving the problem.
Here, '관건이다' is used to indicate that effort is the decisive element in determining success.
성공 여부는 노력의 관건이다.
Success depends on effort.
In this example, '관건이다' conveys the idea that health is essential for a fulfilling life.