- (of organic matter) rot or decompose through the action of bacteria and fungi（有机物质）腐坏, 腐败：
a jelly that rapidly decays into an unpleasant mush
很快会变成臭糊的果冻
as adj. decaying the odour of decaying fish.腐烂的鱼臭味。
- with obj. cause to rot or decompose使腐坏, 使腐烂：
the fungus will decay soft timber.
菌类会使软木材腐烂。
- (of a building or area) fall into disrepair; deteriorate（建筑、地区）坍塌失修, 坏损：
facilities decay when money is not spent on refurbishment.
因为没有花钱整修, 所以设施都受损了。
- decline in quality, power, or vigour衰减,衰微, 衰退：
the moral authority of the party was decaying.
该党的道德权威已日渐衰微。
- Physics (of a radioactive substance, particle, etc.) undergo change to a different form by emitting radiation【物理】（放射性物质、粒子等）衰变：
the trapped radiocarbon begins to decay at a known rate.
陷俘的放射性碳开始以已知速率衰变。
- technical (of a physical quantity) undergo a gradual decrease〈技〉（物理量）衰减：
the time taken for the current to decay to zero.
电流衰减到零所需的时间。
- the state or process of rotting or decomposition腐败, 腐坏, 腐烂：
hardwood is more resistant to decay than softwood
硬木材比软木材耐腐
tooth decay.
牙齿龋蚀。
- structural or physical deterioration破败：
the old barn rapidly fell into decay.
老谷仓很快破败。
- rotten matter or tissue腐败物; 腐烂组织：
fluoride heals small spots of decay.
氟化物可以治愈小面积腐烂。
- the process of declining in quality, power, or vigour衰减, 衰微, 衰退：
the problems of urban decay.
城市衰退的诸多问题。
- Physics the change of a radioactive substance, particle, etc. into another by the emission of radiation【物理】衰变：
the gas radon is produced by the decay of uranium in rocks and soil
气体氡是由岩石和土壤中的铀衰变产生的
count noun he developed a detector for decays of carbon-14.他发明了碳-14衰变探测器。
- technical gradual decrease in the magnitude of a physical quantity〈技〉（物理量的）衰减：
the required time constant for current decay is 1ms.
电流衰减所需的时间常数是一毫秒。