Before revision: It is a dimensionless quantity in materials science and in soil science, and is closely related to the porosity (often noted as , or , depending on the convention), the ratio of the volume of voids () to the total (or bulk) volume (), as follows: in which the total (or bulk) volume () of the soil is the sum of the volume of the solids () and the volume of voids (): and where is the void ratio, is the porosity, VV is the volume of void-space (gases and liquids), VS is the volume of solids, and VT is the total (or bulk) volume.
After revision: It is a dimensionless quantity in materials science and in soil science, and is closely related to , for ideal porous media with a rigid skeleton structure (i.e., without variation of volume when the solid is saturated with water (no swelling); nor shrinking effect after drying of a sample), the porosity (often noted as , or , depending on the convention), the ratio of the volume of voids () to the total (or bulk) volume (), as follows: in which the total (or bulk) volume () of the porous material is the sum of the volume of the solids () and the volume of voids (): and where is the void ratio, is the porosity, VV is the volume of void-space (gases and liquids), VS is the volume of solids, and VT is the total (or bulk) volume.