不可欠
ふかけつ · fukaketsu · JLPT N1 · na-adj
indispensable
不 — single pictograph; bird flying upward
Originally a pictograph in oracle bone script, traditionally interpreted as a bird flying up toward the sky and unable to come down, suggesting negation or refusal. Over time it became the standard negation word in Chinese, used before verbs and adjectives to mean 'not'.
可 — mouth 口 + breath marker 丁 (modified)
可 originally depicted a mouth (口) with a curved stroke suggesting exhaled breath or speech, conveying approval or assent. From this came the meaning 'to permit' or 'can,' as granting permission was expressed verbally. Today it broadly means 'may,' 'can,' or 'approve.'
欠 — person 人 below + open mouth 欠 top (yawning figure)
Pictograph of a person kneeling with mouth wide open, exhaling — originally depicting a yawn or breath. From this came meanings like 'to lack' or 'to owe', as if something is missing or breathed out. It now serves as a radical in characters related to breathing, singing, or desire (歌, 歡, 欲).