And we will have to use no source of energy for this type of movement. This is known as passive diffusion because we are not using energy and we are not using any type of transport protein, integral protein. Now, water is such a common molecule that undergoes path of diffusion that we give it a special type of name. So basically, the passive diffusion of water via a semipermeable membrane is known as osmosis. And in osmosis, water always travels from a high water concentration to a low water concentration or equivalently from a low solved concentration to a high solub concentration. These two statements are exactly equivalent.