误差
wù chā · HSK 7
error
📏 误 mistake + 差 difference = the gap of error; measured value minus true value
误 carries the sense of a mistake or being off; 差 means a difference or discrepancy. Together they name the small gap between a measured result and the true value — the margin of error.
误 — speech radical 讠 + 吴 wú (phonetic)
误 is a semantic-phonetic compound. The left side 讠 (speech) hints at meaning—originally tied to mistaken or misleading words—while 吴 supplies the sound. Over time it broadened from verbal errors to any mistake, delay, or harm caused by error.
差 — 垂 (drooping) + 工 (work/tool)
Originally depicted a hand reaching down to grasp grain stalks of uneven length, suggesting discrepancy or unevenness. From this came the meaning 'difference' or 'to differ.' The reading chā specifically carries the sense of disparity, while other readings developed meanings like 'to dispatch' (chāi) and 'poor/lacking' (chà).