The combination or arrangement of primary soil particles into secondary particles, units, or peds. These peds may be, but usually are not, arranged in the profile in such a manner as to give a distinctive characteristic pattern. The peds are characterized and classified on the basis of size, shape, and degree of distinctness into classes, types, and grades. See also structure classes, soil; structure grades, soil; and structure types, soil. These are defined and tabulated under structure types, soil (Table 3).