Structureless soil material may be either single grains or massive. Soil material of single grains lack structure. In addition, it is very friable, soft or loose. On rupture, more than 50 percent of the mass consists of discrete mineral particles. Massive soil material also lacks structure but differs from single grain in that upon rupture it does not break along any predictable boundary and may result in soil fragments or soil fragments and single grains.
Some soils have simple structure , each unit being an entity without component smaller units.
Others have compound structure , in which large units are composed of smaller units separated by persistent planes of weakness. Field terminology for soil structure consists of separate sets of terms designating each of the three properties, which by combination form the names for structure. Several basic shapes of structural units are recognized in soils. Supplemental statements about the variations in shape of individual peds are needed in detailed descriptions of some soils. The units are flat and platelike.