The word we use for this is mujo, constant change.
The word the Romantic poets liked to use was “Mutability,” the title of a poem by Shelley that begins:
We are as clouds that veil the midnight moon;Read the rest of Richard's Sweeping Zen blog entry, "Change is Balance."
How restlessly they speed, and gleam, and quiver,
Streaking the darkness radiantly!–yet soon
Night closes round, and they are lost forever.