key; crucial; crux
HSK level
关键 (guānjiàn) is a Chinese word functioning as both a noun ('the key, the crux, the decisive point') and an adjective ('crucial, pivotal, key').
It names the single most important factor on which success or an outcome depends (问题的关键 the crux of the problem, 关键时刻 the critical moment, 关键在于 the key lies in). It is register-neutral. For English speakers, a very common and useful structure is 关键是…… / 关键在于…… meaning 'the key is that...' — a way to point out what really matters.
As an attributive it precedes nouns directly (关键人物 key figure, 关键词 keyword). Note that 关键 is abstract and figurative; it never refers to a physical door key, which is 钥匙 (yàoshi). Its literal characters, 'gate + bolt,' capture the idea of the crucial latch that everything hinges on.
Character by character
Memory hook: 关 (gate) + 键 (bolt) = the bolt on the gate — the decisive point everything hinges on.
关键 appears in 4 Fluentide podcast episodes at natural native speed — each with the full Chinese script, pinyin, and line-by-line English translation.
这个问题的关键是钱。
Zhège wèntí de guānjiàn shì qián.
The crux of this problem is money.
spoken
关键时刻他总是很冷静。
Guānjiàn shíkè tā zǒngshì hěn lěngjìng.
He's always calm at the critical moment.
neutral
成功的关键在于坚持。
Chénggōng de guānjiàn zàiyú jiānchí.
The key to success lies in perseverance.
neutral
这项技术在整个项目中起着关键作用。
Zhè xiàng jìshù zài zhěnggè xiàngmù zhōng qǐ zhe guānjiàn zuòyòng.
This technology plays a crucial role in the whole project.
written
关键 is written with 19 strokes (关: 6, 键: 13). Tap replay to watch each character drawn again.
重要 means 'important' — one of possibly many important things. 关键 is stronger: the single decisive factor everything depends on. Many things can be 重要, but the 关键 is the one that determines the outcome.
核心 means 'core / central part' (核心问题 core issue). 关键 stresses the decisive hinge for success or failure. 核心 is about centrality; 关键 is about what tips the result.
钥匙 is a physical door key. 关键 is a figurative 'key' — the crucial point. Never use 关键 for the metal object that opens a lock.
Acquire it by listening
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