1. Dictionary meaning

관건 (關鍵), literal meaning: the bar and the lock that secure a gate.

Figurative meaning: the most important part of an issue, or the deciding factor in solving a problem.

관건이다 = “is the key,” “is what matters most,” “is the deciding factor.”

2. Origin

관건 is a Sino-Korean word made of two characters:

關 (관): the wooden bar placed across a gate to lock it

鍵 (건): a lock, or the bolt of a lock

In the old days, a city gate or house door was only secure if the bar and the lock were in place. They were the single point that decided whether the gate stayed shut or opened. That is how the word came to mean “the crucial point on which everything depends.” The idea is close to the English metaphor of “the key.”

3. How to use it

[Noun] + 이/가 관건이다: “[Noun] is the key.”

관건은 [Noun/clause] + 이다: “The key is ~.”

~느냐가 관건이다: “The key is whether ~.”

💡 Register note: It sounds formal. You’ll see it often in news, reports, analyses, and speeches. In casual conversation, Koreans tend to say “~이/가 제일 중요해” or “~이/가 핵심이야.”

4. Example sentences

이번 경기는 체력이 관건이다.

→ Stamina is the key in this match.

한국어 실력 향상의 관건은 매일 말하는 연습입니다.

→ The key to improving your Korean is practicing speaking every day.