vi.

1. 腐朽，腐爛；蛀蝕
   Sweet potatoes decayed after the frost.

   霜下了之後，地瓜爛掉了。

2. 衰敗；衰退
   The Turkish Empire decayed in the nineteenth century.

   土耳其帝國在十九世紀時衰落。

vt.

1. 使腐朽，使腐爛
2. 使（牙齒）蛀壞
   Sweets can decay the teeth.

   糖果會蛀蝕牙齒。

n.[U]

1. 腐朽，腐爛；蛀牙
   They are figuring out a way to stop the decay of the ancient building.

   他們在想辦法阻止這古老建築的朽壞。

2. 衰敗；衰退
   His mental decay is distressing.

   他的智力衰退令人苦惱。

3. （放射性物質的）蛻變
4. 人造衛星重返大氣層的日期

v.

1. rot or cause to rot through the action of bacteria and fungi; decompose.
   ▸decline in quality or vigour; deteriorate.
2. Physics  (of a radioactive substance, particle, etc.) undergo change to a different form by emitting radiation.

n.

1. the state or process of decaying.
2. rotten matter or tissue.