The process of soil material contracting to a lesser volume when subject to loss of water.

• basic shrinkage phase (or zone) - The middle phase of soil shrinkage between the structural and residual shrinkage; it refers to the fundamental shrinkage process of a specified soil.
• isotropic shrinkage - Shrinkage that occurs equally in all directions.
• moisture ratio - Volume water per volume of soil (m3 m-3).
• ped (shrinkage) - A naturally occurring unit of soil defined by surrounding lines of weakness; the smallest unit of natural soil with no internal shrinkage cracks.
• residual shrinkage - Shrinkage that is less than volume water loss during the final stages of drying.
• shrinkage characteristic - The relationship between the soil volume and volume of water contained in a specified soil mass or ped (m3 m-3).
• shrinkage coefficient - The change in soil bulk volume with change in mass water content at a constant stress; also equivalent to, the rate of change in void ratio with moisture ratio at a constant stress.
• structural shrinkage - Shrinkage that is less than volume water loss due to water drainage from macropores at high soil water content.
• surface subsidence - See shrinkage, soil, vertical shrinkage.
• swelling hysteresis - See hysteresis.
• unidimensional shrinkage or 1-D shrinkage - Shrinkage that occurs exclusively in the vertical direction.
• unitary shrinkage - Shrinkage which is equivalent to the change in water volume.
• vertical shrinkage - The shrinkage-induced length change of a soil in the vertical direction, also called surface subsidence if it occurs exclusively at the soil surface.