Parameter Tree:
EARTH SCIENCE > LAND SURFACE > SOILS > SOIL STRUCTURE

Definition:
The combination or arrangement of primary soil particles into secondary
units or peds. These secondary units may be, but usually are not, arranged
in the profile in such a manner as to give a distinctive characteristic
pattern. The secondary units are characterized and classified on the
basis of size, shape, and degree of distinctness into classes, types, and
grades, respectively. 


Reference:
The Nature and Properties of Soils, Prentice Hall, 1996.