fluidity

Fluidity is a quality of being graceful or flowing, like the fluidity of a dancer’s movements.

Things that move with easy, smooth motions have fluidity — think of clouds moving across the sky on a windy day, or the way a modern dancer’s body moves. This adjective can also mean “changeable,” like the fluidity of ideas being exchanged during a high school debate class. As a physical quality, you might also describe the fluidity of any substance that’s fluid, or behaves like a liquid.