腐烂
fǔ làn · HSK 7
to rot
🍂 腐 (rot) + 烂 (mushy/decayed) = rotten-mushy, fully decayed
腐 means rot or spoiled (also in 豆腐 tofu, 'bean curd'); 烂 means mushy, overripe, or falling apart. Together they double down on the idea: thoroughly rotten, used both literally for food and figuratively for corruption.
烂 — fire radical 火 + 阑 (lán, phonetic)
A semantic-phonetic compound: 火 (fire) gives the meaning, while 阑 supplies the sound 'lán'. The original sense was 'cooked soft by fire,' as in overboiled food falling apart. From there it extended to 'rotten, mushy, worn out,' and figuratively to 'lousy' or 'terrible.'