伝染
でんせん · densen · JLPT N2 · noun
contagious disease
🦠 伝 (pass on) + 染 (stain): illness that passes from person to person
Compound of 伝 (to transmit, tsutaeru) and 染 (to dye or stain, somaru). The word names an illness spreading from one person to another.
染 — water 氵 + nine 九 + wood 木
染 depicts the dyeing process: 氵 (water) for the dye liquid, 木 (wood) for plant-based dyestuffs, and 九 (nine) suggesting repeated dippings to deepen the color. Originally meaning 'to dye cloth,' it later extended to figurative senses like 'to be influenced' or 'to contract' (as in illness).