Like many important Buddhist words, anicca points to what something is not rather than to what it is. The Sanskrit word nitya (spelled nicca in Pali) denotes what is constant, perpetual, and therefore eternal. It has the sense of something being regularly occurring, or always occurring in a regular manner.
When the prefix a- is added, the meaning is reversed. Thus the Buddhist term anitya, or anicca, which is almost always translated as “impermanent,” might be more precisely rendered “inconstant” or “changeable.” It recognizes that human experience is always changing, becoming something different than it is, and uncovers the truth that because of this it is unstable.
For example, in the early Buddhist texts, gratification is commonly said to be found in things such as the sense organs and their corresponding objects, since they can give rise to both physical and mental pleasure. But there is also a danger inherent in them because they inevitably change and become something other—they are inconstant and unreliable. The only solution or escape from this limitation is the removal of desire for such changeable things.
In the Buddha’s very first discourse, he pointed to the impermanence of all phenomena and revealed that because of this inconstancy, everything is ultimately unsatisfying and tainted with suffering. The gratification we find in things is sure to collapse as they change.
This is the reason nothing is fit to be regarded as constituting or belonging to a consistent self. The core Buddhist teaching of nonself is not so much stating that a self does not exist as it is identifying the self as being as impermanent, inconstant, and unsubstantial as every other conditioned thing.
Insight into these three characteristics of phenomena—impermanence, suffering, and nonself—lies at the heart of wisdom. Giving careful attention to the perception of impermanence is thus an important practice for developing this wisdom.
In mindfulness meditation one closely observes the arising and passing away of bodily sensations, feeling tones, states of mind, and mental objects, thereby discerning their impermanence. You can actually see for yourself how the mind is “moving and tottering, impermanent, changing, becoming otherwise,” as one text (Samyutta Nikaya 35.93) puts it, by simply looking inward.
Perhaps the most intimate and profound encounter any of us can have with the truth of impermanence is the recognition of how fleeting, and thus precious, this human life—even this very moment—actually is.