算数
さんすう · sansuu · JLPT N2 · noun
arithmetic
🧮 算 = count, 数 = number: counting numbers, i.e. arithmetic
算 (san) means to calculate or count, and 数 (sū) means number. Put together they name the act of working with numbers: 'sansuu' is the school subject of arithmetic.
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'.
数 — 婁 (lóu, phonetic) + 攵 (action radical)
数 is a phono-semantic compound. The right side 攵 (a hand holding a stick) suggests an action, originally tallying or counting by striking marks. The left side 婁 supplies the sound. Over time the meaning broadened from 'to count' to 'number' and 'several'.