密切
mìqiè · HSK 4
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🤝 密 = secret/dense + 切 = cut/close; together = closely-knit, intimate
密 carries the sense of dense or tight (as in 秘密 secret), and 切 means to cut or press close against. Joined, 密切 describes a bond pressed tight with no gap — close ties, intimate cooperation.
密 — 宀 roof + 必 (phonetic) + 山 mountain
Originally referring to a hidden, sheltered place in the mountains, 密 combines 宀 (roof/cover) over 必 (phonetic) with 山 (mountain) at the base. The meaning extended from 'secluded mountain hideaway' to 'dense, close, secret'. Today it commonly means dense, intimate, or secret.
切 — 七 (phonetic) + 刀 (knife radical)
切 is a semantic-phonetic compound: 刀 'knife' gives the meaning of cutting, while 七 supplies the sound. The original sense was to slice or cut with a blade. From there it extended figuratively to 'close to' (as in pressed against) and 'urgent/earnest', as in 切实.