damage, remain, slight
戔 centers on reduction through harm: damage that makes something less, leaving only a slight remainder. The meanings 'damage', 'remain', and 'slight' connect as the result of cutting or wounding.
戔 is composed of two 戈 (halberd) elements, suggesting conflict or cutting that leads to damage and reduction. The exact historical development is uncertain, but the doubling of a weapon component likely reinforces the idea of harm.
Two halberds (戈) clash, causing damage. After the fight, only a slight remnant remains.
For セン, imagine a scene of damage where a cent (coin) is all that remains: cent -> セン, and the slight remainder is just one cent.
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