This term means lack of permanence. Everything in the world comes into being through a combination of causes and conditions. It perishes without them. There is no permanent, unchanging essence which one may see as the basis of its identity. Buddhism distinguishes two levels of impermanence. First, impermanence of successive appearance: A living individual lacks any essence, such as that of a soul, which does not change in a succession of birth and death. Continuity and similarity are mere appearance. Second, impermanence of every thought-instance: It emphasizes that everything which has arisen from the combination of causes and conditions changes, arises and is extinguished in the instant of a thought.

Our body is the same. It is but maintained by skin and bones. It whirls with the wind of one's thoughts. Every instant it arises and is extinguished. It is impermanent and empty. There is no creator, abuser or victim, because it is always empty after all. But due to wrong understanding and total confusion, a common man sticks to things that actually do not exist.

(The Treatise on the Great Perfection of Wisdom)