Many search for environmental dictionary. In this page, all the environmental related key words and definitions are given. This will help who wants to understand environment related issues more deeply and in sophisticated way. The terms have been written in clear, simple language that is understandable even to non-specialists but is consistent with the complexity of the term itself. The terms are given alphabetically. Let’s see…..






A measure is taken for reducing or eliminating air or noise pollution, which may involve legislative proceedings and technological applications.


Non-biological ; thus an abiotic element is a physical or chemical feature of an ecosystem or environment.


Refers to the non-living components of the environment.


The removal of a surface layer, especially used for the melting and evaporation of the surface of ice, and also for the removal of loose surface material by the wind (deflation).

in other words Ablation is a Combined processes (such as melting, sublimation, and evaporation) which remove snow or ice from a glacier or from a snow field; reduction of the water equivalent by melting, evaporation, wind and avalanches.


Refers to the abbreviation of alkyl benzene sulphonate.


Absolute Humidity:

The weight of the water vapor found in a unit volume of air. In the metric system, it may be defined as the number of grams of water vapor in a cubic meter of air.



Absolute Age:

The age of rock, mineral or fossil in years. It is found out as a radiometric age or by counting varies. Radiometric dating involves experimental errors, so such dates are usually expressed as a plus or minus error.



(1) A black material which absorbs heat from sunlight.

(2) An apparatus used in the process in which one material is employed to retain another.
Absorber are used for removing a gaseous or liquid material selectively from another gas or liquid. Usually, the process is performed in cylindrical towers packed with an absorbing material.


Absorber Plate:

A black-painted, flat piece of metal which absorbs sunlight, transforms it to heat by absorption, and in turn, radiates heat into the surrounding air and the cover. The absorber plate in a fluid-medium collector is usually constructed differently as it must contain the conduit or piping-circuit medium in the absorber. There are many designs, with copper and aluminum being the two most commonly used metals.



Absorbing Duct:

A tube which is used in a ventilator system for attenuating sound waves while offering low resistance to a continuous flow of air.




Refers to the ratio of the radiant flux absorbed by a body to that which is incident upon it.

Absorption Chiller:

A refrigeration system which is used in the solar cooling of buildings, where sun-heated water, usually above 80°C, provides the operating energy.

Absorption Coefficient:

(1) It Refers to the ratio of the sound energy absorbed by a surface of a medium (or material) revealed to a sound field (or to sound energy incident on the surface). The stated values of this ratio hold for an absolute area of the surface. The requirements under which measurements of absorption coefficients are made have to be started explicitly.

(2) A measure of the amount of usually incident radiant energy absorbed through a unit distance or by a mass of absorbing medium; also, the maximum volume of gas that can be dissolved in a unit volume of water. The absorption coefficient of gases has been found to decrease with increasing temperature and salinity.

(3) The fractional decrease in the intensity of an x-ray or gamma-ray beam per unit thickness (linear consumption coefficient), per unit mass (mass absorption coefficient), or pet atom (atomic absorption coefficient) of the absorber, caused by the disposition of energy in the absorber. The total absorber coefficient has been based on the sum of the individual energies.

Absorption Coefficient, Atomic:

Refers to the linear absorption coefficient of a nuclide. It is equivalent to the nuclide’s total cross section for the given radiation.

Absorption Coefficient, Compton:

Refers to the fractional decrease in the energy of an x-ray or gamma-ray beam which is caused by the deposition of the energy to electrons produced by the Compton effect in an absorber.

Absorption Coefficient, Mass:

Refers to the linear absorption coefficient per centimeter divided by the density of the absorber in grams per cubic centimeter. It is expressed as ū/p where ū is the linear absorption Coefficient and p the absorber density.


Absorption Equipment, Floating Bed Scrubber:

A floating-bed —sieve-tray arrangement. Low-density spherical packing is kept on the sieve tray so that the gas bubbles rise through the wetter sphere. This system is advantageous for use with gas streams having particulate matter because the fluidized character of the bed of spheres prevents the buildup of a particulate sludge.
Absorption Equipment, Packed Towers: A packed tower is a vertical, cylindrical shell which is packed with solid objects which maximize the gas—liquid interfacial area at low resistance to gas flow. Packing such as Raschig rings, Berl saddles; Pall rings, Intaloz saddles, and Tellerettes may be used. The liquid enters at the top of the tower and gets distributed over the packing with spray nozzle, weirs, or perforated plates. The gas is allowed to enter at the bottom of the tower.

Absorption Equipment, Plate or Tray Towers:

Plate or tray towers have horizontal plates or trays, usually in a cylindrical shell. Sieve plates and bubble cap plates are used in plate towers. The gases flow upward and bubble through the perforations in the bubble cap or sieve plate. The liquid flows downward through an overflow plate. The gas is prevented from flowing up the liquid downflow by keeping the pipe exit below the level of the pool of liquid on the plate. The bubbles provide the gas—liquid interfacial area through which the mass transfer takes place.

Absorption Equipment, Spray Towers:

Spray towers have a much smaller gas—liquid interfacial area than packed or plate towers. The liquid is made to introduce through spray nozzles and flows countercurrent, crosscurrent, or co-current with the gas, depending on the design. The pressure drop through a spray tower has been substantially less than through either packed or plate towers.

Absorption Equipment Venturi Scrubbers:

A co-current process in which the liquid is entering in or near the Venturi’s throat and flowing with the gas into an entrainment separator. Venturi scrubbers do not appear to be best suited for the removal of pollutant gases.

Absorption Factor:

it Refers to the ratio of the intensity loss by absorption to the total original intensity of radiation.

Absorption Pit, Seepage P, Absorption Well, Dumb Well, Soak-away:
A hole in the ground for disposal of rainwater, sullage Or treated sewage effluent. It is dug in country districts where there is porous soil, a water table not less than 2 m below ground and no other danger of contaminating water supplies.

Absorption loss:

Absorption loss is the loss of water by infiltration from a canal, reservoir or other body of water or from a field during the process of priming.


Absorption Rate:

For surfaces, it refers to the energy absorbed per unit area per unit time. It is revealed in the same units as emissive power.


Absorption specific:

(1) Quantity of water recharged into a recharge well per unit time and per unit rise of head.


(ii) Ratio of the quantity of water which can be absorbed by soil which contains retained water only, to the total amount of water when fully saturated, or to total soil volume.



Aeration is the rate of amount of infiltrated water per unit area and time.


Advection is the Process of transfer of air-mass properties by the velocity field of the atmosphere.


The gradual Addition of new bad to by the deposition of sediment carried by the water of a stream.


Albedo Ratio of reflected to incoming radiation usually given in percent.

 Annual Flood:

The highest peak discharge in a water year.

Antecedent Precipitation:

Antecedent Precipitation means rainfall that occurs a given number of days prior to the particular rain storm under consideration.