腐烂 (fǔ làn): 썩다.

In summer, if you forget fruit outside the fridge, it starts to rot after two days and gives off a bad smell.

The trunk of that old tree had already rotted; the firefighters worried it would be blown down in a strong wind, so they sawed it down.

If you don't clean the wound properly, bacteria can cause an infection and even make it rot.

The wooden box in the corner of the kitchen had been damp for a long time, so its bottom had rotted and it could no longer be used to hold things.

The rotting fish on the beach attracted swarms of flies, so the workers had to bury it in the sand.