誤差
ごさ · gosa · JLPT N1 · noun
mistake
📏 誤 = mistake + 差 = difference: the gap between a measured value and the true value
誤差 is used in science and measurement for the amount a result is off from the correct value. The same 誤 appears in 誤解 (misunderstanding), so 誤 always signals something gone wrong.
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).