扣除
koù chú · HSK 7
to deduct
➖ 扣 deduct/withhold + 除 remove = deduct an amount
扣 (kòu) means to withhold or hold back, and 除 (chú) means to remove or take away. Together they describe subtracting a sum, like when taxes are taken out of pay.
扣 — hand radical 扌 + 口 (mouth/phonetic)
扣 is a phono-semantic compound: the hand radical 扌 signals an action done with the hand, while 口 (kǒu) supplies the sound. Its core sense is to knock, fasten, or buckle with the hand, later extending to deduct (as in deducting points) and to button up.
除 — left ear/mound 阝 + surplus 余
除 combines the 'mound/steps' radical 阝 (originally 阜, a hill) with 余 as the phonetic. It first meant the steps of a palace, then extended to 'remove' or 'clear away' (as one sweeps steps clean), and later to mathematical 'divide.'