Question

classification of soil.

Answer 1

Soil classification is also know as soil taxonomy. The Unified classification system of the soil is one among the commonly used systems.
soil is broadly classified into 4 categories mainly.
1. finely grained
2. coarse
3. organic soil
4. peat

thus, the criteria used here is particle size. however, there can be other criterions used to classify soil such as shape of the soil particle, composition of the soil, colour of the soil etc.