Gradual absorption is a process that can be described by the term osmosis. Osmosis is the movement of molecules from an area of higher concentration to an area of lower concentration, through a semi-permeable membrane. This process is used in many biological and chemical processes, such as the absorption of water by plants and the absorption of nutrients by cells. Gradual absorption occurs when the molecules move slowly, allowing for a gradual increase in the concentration of the molecules in the area of lower concentration.