温暖
おんだん · ondan · JLPT N3 · na-adj
warmth
♨️🔥 温暖 = warm + warm: two kanji for warmth stacked together
Both kanji mean warm. 温 (on) is the on of onsen 温泉, hot spring. 暖 (dan) is the dan of danbō 暖房, room heating. Add 地球 (earth) and 化 (change) and you get 地球温暖化, global warming.
暖 — sun radical 日 + 爰 (yuán, phonetic)
暖 is a semantic-phonetic compound. The 日 'sun' radical carries the meaning of warmth, while 爰 supplies the sound (historically close to 'nuǎn'). It originally described the warmth of sunlight and broadened to mean 'warm' in general — both physical heat and figurative warmth like kindness.