Unit Weight is the ratio of weight to volume. It is also known as the specific weight. And Density is the ratio of Mass to volume.

Degree of Saturation is defined as the ratio of the volume of water to the volume of voids present in a given soil mass. It is represented as ‘s’.

Void Ratio is defined as the ratio of the volume of voids (Vv) to the volume of solids(Vs) present in a given soil mass. It is represented as ‘e’. Porosity (η): It is defined as the ratio of the volume of voids(Vv) to the volume of soil (V) present in the given soil mass. It is represented as ‘η’.

Water present in the soil in any form is termed soil water. Many types of sοil water: Ground (Free, Gravity) water, Capillary water, Structural water, and Adsorbed water.

The various techniques for determining the water content of soil are as follows: Oven Drying Method, Sand Bath Method, Alcohol Method, Pycnometer Method, Calcium Carbide or Moisture Meter Method, Radiation Method, and Torsional Balance Method.

Water content (w):It is define as the weight of water to the weight of solids present in the given soil mass. Moisture content (m): It is define as the mass of water to the mass of solids present in the given soil mass. The  result of water content & moisture content are same .

Soil is a three-phase system that consists of solid, liquid & gaseous matter, that do not occupy separate spaces, but are blended with each other in a definite proportion, which in turn governs the properties 0f soil.

There are many types of soil. Examples – Alluvial soil, Lacustrine soil, Marine soil, Aeolian soil, Glacial soil, Colluvial soil, Loess soil, Marl soil & others.

The process of formation of soil is termed as PEDOGENESIS. Soil is formed due to the weathering (erosion /wear and tear) of rocks. Weathering of rock can occur either physically or chemically.