(Sanskrit: anitya, Pali: anicca) This term refers to the Buddhist notion that all things of samsara are impermanent. Once created, they decay and pass away. Although this is particularly true for human illness and death, the idea refers to the nature of all things. It is one of the reasons for suffering and is considered one of the three marks of existence.

Nothing remains the same for two consecutive moments. Heraclitus said we can never bathe twice in the same river. Confucius, while looking at a stream, said, "It is always flowing, day and night." The Buddha implored us not just to talk about impermanence, but to use it as an instrument to help us penetrate deeply into reality and obtain liberating insight. We may be tempted to say that because things are impermanent, there is suffering. But the Buddha encouraged us to look again. Without impermanence, life is not possible. How can we transform our suffering if things are not impermanent? How can our daughter grow up into a beautiful young lady? How can the situation in the world improve? We need impermanence for social justice and for hope. Aware of impermanence, you become positive, loving and wise. Impermanence is good news. Without impermanence, nothing would be possible. With impermanence, every door is open for change. Impermanence is an instrument for our liberation. Thich Nhat Hanh

the property of not existing for indefinitely long durations

The gross and subtle levels of the transience of phenomena. The moment things and events come into existence, their disintegration has already begun.

One of the three marks of existence, referring to the transitory nature of all composite phenomena.

Impermanence (Sanskrit: अिनत्य anitya; Pāli: अिनच्च anicca; Tibetan: mi rtag pa; Chinese: wúcháng; Japanese: 無常 mujō) is one of the essential doctrines or three marks of Buddhism. The term expresses the Buddhist notion that everything, without exception, is constantly in flux, even planets, stars and gods. Human life embodies this flux in the ageing process, the cycle of birth and rebirth (samsara), and in any experience of loss.