添
tiān · HSK 6
add
💧 氵water + 天 sky + 心 heart — stacking parts means adding more
天 (tiān) sits inside and supplies the pronunciation. The water radical suggests pouring in extra. The whole character embodies addition — heaping one thing on top of another.
添 — water radical 氵 + 忝 (phonetic)
添 is a phono-semantic compound. The water radical 氵 hints at the meaning 'to add water, to pour in more,' while 忝 supplies the sound. From the literal sense of topping up liquid, it broadened to mean 'to add' or 'to append' anything.