Impermanent means not staying the same forever — it can change, fade, or end. A job, a feeling, a mark on a window, even a building made to last only a season can be impermanent. It is the adjective; impermanence is the noun (the fact of not lasting). It is a little formal. In everyday talk people more often say temporary, or not permanent. Though actually, temporary often means “we planned it to be short.” Impermanent can also mean we hoped it would last, but nothing does — a softer, more honest word.