拡散
かくさん · kakusan · JLPT N1 · noun
diffusion
🌼 拡 = expand + 散 = scatter: together, spreading outward and scattering apart
拡 means expand or widen, and 散 means scatter or disperse. Together they describe something spreading outward and breaking apart, such as ink diffusing through water or dandelion seeds carried away by the wind.
散 — 月 (meat) + 攵 (action) + 卄 (hemp fibers)
Originally depicted beating hemp fibers apart with a stick, with 月 (meat/flesh) added later. The core image of separating or scattering things gave rise to meanings like 'scatter,' 'disperse,' and 'loose/leisurely.' The 攵 component signals an action done by hand.