After a substance has spread evenly through a space, molecules keep moving but there is no net movement. What is this state called?

1. Once a substance has diffused completely through a space, its concentration gradient is gone. 2. Molecules still move around in that space, but there is no net movement of molecules from one area to another. 3. This lack of a concentration gradient with no net movement is dynamic equilibrium. 4. Osmotic pressure and selective permeability describe other properties, and facilitated transport is a protein-assisted route across the membrane. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 5 "Structure and Function of Plasma Membranes", section 5.2 Passive Transport_