方程式
ほうていしき · houteishiki · JLPT N2 · noun
equation
⚖️ 方程 (equation) + 式 (formula) = a formula where both sides balance
方程 comes from ancient Chinese math, where counting rods were laid out in rows to solve for unknowns. Read it as equation-formula: an expression whose two sides must stay equal across the equals sign.
方 — pictograph of a plow or two boats joined side by side
方 originated as a pictograph, traditionally interpreted as a plow handle or two boats lashed together. From the idea of paired boats it extended to mean 'side by side,' then 'square,' 'direction,' and 'region.' It was later borrowed for the abstract sense of 'method' or 'way.'
式 — 工 (work) + 弋 (phonetic)
式 is a phono-semantic compound: 工 ('work, craft') gives the meaning of a tool, rule, or method, while 弋 supplies the sound. It originally referred to a standard pattern or model used in craftsmanship, then broadened to mean 'style, form, ceremony, or formula.'