Definition (Oxford Learner’s Dictionary): to decay, or make something decay, naturally and gradually [（使）腐烂，逐渐衰弱（或憔悴）。指蔬菜水果或肉类的分解、腐烂。通常只能表示“有机体腐烂”的过程]

示例：

The meat will rot if it isn't kept cool.

肉如果不冷藏就会腐败。

Too much sugar will rot your teeth.

吃糖太多，就会出现蛀牙。

Definition (Oxford Learner’s Dictionary): decay (something) to be destroyed gradually by natural processes; to destroy something in this way [通常指由良好或完美的状态自然而缓慢地变坏或完全变坏腐烂，或部分地毁坏。在表示“腐烂”的时候，除了有机体以外，还可以描述无生命物体的腐朽。]

示例：

This stone building has decayed over hundreds of years.

这座石头建筑几百年来已经渐渐腐朽。

Element 43 has a very fast rate of decay.

43号元素的衰变速度非常快。

Definition (Oxford Learner’s Dictionary): to be destroyed gradually after death by natural processes [侧重指动物或植物类物体由于内部组织的分解而导致的腐烂过程]

示例：

When they die, they decompose.

当它们死亡，它们就会分解。

As the waste materials decompose, they produce methane gas.

废物腐烂时会产生沼气。