Separation of a solid and a liquid by using a porous substance that only lets the liquid pass through.Filtration occurs during a process when solids are separated from gases or liquids by utilizing a filter medium that permits the flow of fluid to pass through but prevents the solid from doing so. Filtration can be applied in various fields where filters are used, which include physical, mechanical, or biological applications. As discussed in another page within our terminology section, the fluid that passes through the filters is referred to as filtrate.