割算
わりざん · warizan · JLPT N2 · noun
division
割 — 害 (harm, phonetic) + 刂 (knife radical)
A semantic-phonetic compound: the knife radical 刂 gives the meaning 'cut,' while 害 supplies the sound. The original sense was to cut or slice with a blade, which extended to 'divide' and 'allot a share.' Modern uses like 割爱 (give up something dear) preserve this idea of cutting away.
算 — bamboo 竹 + abacus 具 (eye 目 + two hands 廾)
Originally depicted counting with bamboo rods on an abacus-like device. The top 竹 (bamboo) refers to the bamboo counting sticks used in ancient Chinese arithmetic, while the bottom shows hands manipulating them. The meaning broadened from 'to count' to 'to calculate' or 'to plan'.