What is the difference between ROCK, SOIL AND SAND

1. A rock is a naturally occurring aggregate of minerals and/or mineraloids. The Earth's crust (including the lithosphere) and mantle are formed of rock.
http://en.wikipedia.org/wiki/Rock_%28geology%29

2. Soil, comprising the pedosphere, is positioned at the interface of the lithosphere with the biosphere, atmosphere, and hydrosphere. It consists of mineral and organic matter, including living organisms. Soil formation, or pedogenesis, is the combined effect of physical, chemical, biological, and anthropogenic processes on soil parent material resulting in the formation of soil horizons.
http://en.wikipedia.org/wiki/Soil

3. Sand is a granular material made up of fine rock particles. Sand is a naturally occurring, finely divided rock, comprising particles or granules ranging in size from 0.0625 (or 1⁄16 inch) to 2 millimeters. An individual particle in this range size is termed a sand grain.
http://en.wikipedia.org/wiki/Sand

ROCKS (large structure)
↓(weathering)
SANDS (fine structure, relatively uniform particle sizes, cohesionless)
↓(further decomposing)
SOILS (usually very fine structure, uniformed or mixed particle sizes, usually cohesive, sometimes with organic matters)

ROCKS are classified into 3 types: IGNEOUS ROCKS, SEDIMENTARY ROCKS and METAMORPHIC ROCKS.
Rocks are considered as major component of earth surface and have a large continuous structure. Small isolated rocks are considered as STONES.
Something in between stones and sands are COBBLES and GRAVEL.
Rocks will, upon weathering, decompose into finer particles into SANDS and SOILS.
Sands are of particle size of range from 2~0.06 mm, the particles sizes of the same type of relatively uniform and sands are usually classified according to the particle size: COARSE SAND, MEDIUM SAND and FINE SAND. Sands are cohesionless.
The classification of soil is much more complicate because soils are composed of a large variety of particles of different size and , sometimes, organic matters ( peat soil). Usually, it is considered as soil if the major particle size is less than 0.06mm and hence cohesive in nature.
In fact, sands are only classified as a special type of soil ( under the type COHESIONLESS SOIL).

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