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  • Glossary
| Last Updated:02/03/2021



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planting new forests on lands that have not been recently forested.


solid or liquid particles suspended within the atmosphere

adaptive radiation

closely related species that look very different, as a result of having adapted to widely different ecological niches

acid rain

rain or other forms of precipitation that is unusually acidic.

Absorption pit

a hole dug in permeable ground and filled with broken stones or granular material and usually covered with earth allowing collected water to soak into the ground.

arable land

land that can be used for growing crops


the cultivation of aquatic organisms under controlled conditions


not requiring air or oxygen; used in reference to decomposition processes that occur in the absence of oxygen


the process of an organism adjusting to chronic change in its environment.


one substance taking up another at its surface


a characteristic of an organism that has been favoured by natural selection

acid mine drainage

the outflow of acidic water from metal mines or coal mines.


requiring air or oxygen; used in reference to decomposition processes that occur in the presence of oxygen


one substance taking in another, either physically or chemically.


with abnormally low levels of oxygen


man-made, not natural


feathers in the armpit at the base of the under wing.


reflectance; refers to the ratio of light from the Sun that is reflected by the Earth's surface, to the light received by it. Unreflected light is converted to infrared radiation (heat), which causes atmospheric warming (see "radiative forcing"). Thus, surfaces with a high albedo, like snow and ice, generally contribute to cooling, whereas surfaces with a low albedo, like forests, generally contribute to warming. Changes in land use that significantly alter the characteristics of land surfaces can alter the albedo

air pollution

the modification of the natural characteristics of the atmosphere by a chemical, particulate matter, or biological agent.


(sustainability) an ecologically based farming system, that, through the integration of trees in farms, increases social, environmental and economic benefits to land users.


as defined in the book of the same name[1] 1. the bloated, sluggish and unfulfilled feeling that results from efforts to keep up with the Joneses. 2. an epidemic of stress, overwork, waste and indebtedness caused by dogged pursuit of the Australian dream. 3. an unsustainable addiction to economic growth. The traditional Western environmentally unfriendly high consumption life-style: a play on the words affluence and influenza cf. froogle, freegan.


non-living chemical and physical factors of the environment (see also biotic)


a bed or layer yielding water for wells and springs etc.; an underground geological formation capable of receiving, storing and transmitting large quantities of water. Aquifer types include: confined (sealed and possibly containing “fossil” water); unconfined (capable of receiving inflow); and Artesian (an aquifer in which the hydraulic pressure will cause the water to rise above the upper confining layer).

appropriated carrying capacity

another name for the Ecological Footprint, but often used in referring to the imported ecological capacity of goods from overseas

anaerobic digestion

the biological degradation of organic materials in the absence of oxygen to yield methane gas (that may be combusted to produce energy) and stabilised organic residues (that may be used as a soil additive).


(sustainability) the first step in the waste hierarchy where waste generation is prevented (avoided).

available water capacity

– that proportion of soil water that can be readily absorbed by plant roots.

application efficiency

(sustainability) the efficiency of watering after losses due to runoff, leaching, evaporation, wind etc


spiritual philosophy based on the teachings of Rudolf Steiner (25 February 1861 – 30 March 1925) which postulates the existence of an objective, intellectually comprehensible spiritual world accessible to direct experience through inner development - more specifically through cultivating conscientiously a form of thinking independent of sensory experience. Steiner was the initiator of biodynamic gardening


with abnormally low levels of oxygen

alternative fuels

fuels like ethanol and compressed natural gas that produce fewer emissions than the traditional fossil fuels


composite blend of materials made under special conditions. Metal alloys like brass and bronze are well known but there are also many plastic alloys

algal bloom

the rapid and excessive growth of algae; generally caused by high nutrient levels combined with other favourable conditions. Blooms can deoxygenate the water leading to the loss of wildlife


an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions.


general name for the layer of gases around a material body; the Earth's atmosphere consists, from the ground up, of the troposphere (which includes the planetary boundary layer or peplosphere, the lowest layer), stratosphere, mesosphere, ionosphere (or thermosphere), exosphere and magnetosphere.

available energy

energy with the potential to do work

Air Conditioner

A device for conditioning air in an interior space. A Room Air Conditioner is a unit designed for installation in the wall or window of a room to deliver conditioned air without ducts. A Unitary Air Conditioner is composed of one or more assemblies that usually include an evaporator or cooling coil, a compressor and condenser combination, and possibly a heating apparatus. A Central Air Conditioner is designed to provide conditioned air from a central unit to a whole house with fans and ducts.

Air-Source Heat Pump

A type of heat pump that transfers heat from outdoor air to indoor air during the heating season, and works in reverse during the cooling season


Aam Aadmi Party

Air Register

The component of a combustion device that regulates the amount of air entering the combustion chamber

Air Pollution Control

The use of devices to limit or prevent the release of pollution into the atmosphere

Air Infiltration Measurement

A building energy auditing technique used to determine and/or locate air leaks in a building shell or envelope

Adaptation Fund

The Adaptation Fund was established to finance concrete adaptation projects and programmes in developing countries that are particularly vulnerable and are Parties to the Kyoto Protocol. The Fund is to be financed with a share of proceeds from clean development mechanism (CDM) project activities and receive funds from other sources.

Amorphous Semiconductor

A non-crystalline semiconductor material that has no long-range order


Primitive plants, usually aquatic, capable of synthesizing their own food by photosynthesis.


A measure of the flow of current (in amperes) over one hour

Alternative Fuels

A popular term for "non-conventional" transportation fuels derived from natural gas (propane, compressed natural gas, methanol, etc.) or biomass materials (ethanol, methanol).

Acid Rain

A term used to describe precipitation that has become acidic (low pH) due to the emission of sulfur oxides from fossil fuel burning power plants.


The passing of a substance or force into the body of another substance

Absolute Humidity

The ratio of the mass of water vapor to the volume occupied by a mixture of water vapor and dry air.


Air and Waste Management Association, a professional organization of people involved in air pollution control and solid waste management, from both the public and private sectors. For more information, see AWMA's website

attainment area

A geographic area that the US EPA has designated as meeting the NAAQS for a specified pollutant. (See nonattainment area.)

Active Power

The power (in Watts) used by a device to produce useful work. Also called input power.


In a solar thermal system, the ratio of solar energy striking the absorber that is absorbed by the absorber to that of solar energy striking a black body (perfect absorber) at the same temperature. The absorptivity of a material is numerically equal to its emissivity.

Absorption Coefficient

In reference to a solar energy conversion devices, the degree to which a substance will absorb solar energy. In a solar photovoltaic device, the factor by which photons are absorbed as they travel a unit distance through a material


The component of a solar thermal collector that absorbs solar radiation and converts it to heat, or, as in a solar photovoltaic device, the material that readily absorbs photons to generate charge carriers (free electrons or holes).


A material that extracts one or more substances from a fluid (gas or liquid) medium on contact, and which changes physically and/or chemically in the process. The less volatile of the two working fluids in an absorption cooling device


Asbestos Hazards Emergency Response Act, Title 2 of the Toxics Substances Control Act


The positive pole or electrode of an electrolytic cell, vacuum tube, etc. (see also sacrificial anode).


An instrument for measuring the force or velocity of wind; a wind gauge

Anaerobic Bacteria

Microorganisms that live in oxygen deprived environments

Atmospheric Pressure

The pressure of the air at sea level; one standard atmosphere at zero degrees centigrade is equal to 14.695 pounds per square inch (1.033 kilograms per square centimeter).


An opening; in solar collectors, the area through which solar radiation is admitted and directed to the absorber.

Angstrom Unit

A unit of length named for A.J. Angstome, a Swedish spectroscopist, used in measuring electromagnetic radiation equal to 0.000,000,01 centimeters

Anaerobic Digestion

The complex process by which organic matter is decomposed by anaerobic bacteria. The decomposition process produces a gaseous byproduct often called "biogas" primarily composed of methane, carbon dioxide, and hydrogen sulfide

Anthracite (coal)

A hard, dense type of coal, that is hard to break, clean to handle, difficult to ignite, and that burns with an intense flame and with the virtual absence of smoke because it contains a high percentage of fixed carbon and a low percentage of volatile matter

Angle of Incidence

In reference to solar energy systems, the angle at which direct sunlight strikes a surface; the angle between the direction of the sun and the perpendicular to the surface. Sunlight with an incident angle of 90 degrees tends to be absorbed, while lower angles tend to be reflected

Average Cost

The total cost of production divided by the total quantity produced

Axial Flow Turbine

A turbine in which the flow of a steam or gas is essentially parallel to the rotor axis


An architectural element for shading windows and wall surfaces placed on the exterior of a building; can be fixed or movable

Automatic (or Remote) Meter Reading System

A system that records the consumption of electricity, gas, water, etc, and sends the data to a central data accumulation device

Average Demand

The demand on, or the power output of, an electrical system or any of its parts over an interval of time, as determined by the total number of kilowatt-hours divided by the units of time in the interval

Axial Fans

Fans in which the direction of the flow of the air from inlet to outlet remains unchanged; includes propeller, tubaxial, and vaneaxial type fans

Axial Flow Compressor

A type of air compressor in which air is compressed in a series of stages as it flows axially through a decreasing tubular area

Auxiliary Energy or System

Energy required to operate mechanical components of an energy system, or a source of energy or energy supply system to back-up another

Attic Vent

A passive or mechanical device used to ventilate an attic space, primarily to reduce heat buildup and moisture condensation.


An interior court to which rooms open


The abbreviation for American Wire Gauge; the standard for gauging the size of wires (electrical conductors).

Active Cooling

The use of mechanical heat pipes or pumps to transport heat by circulating heat transfer fluids

Absorption Refrigeration

A system in which a secondary fluid absorbs the refrigerant, releasing heat, then releases the refrigerant and reabsorbs the heat. Ammonia or water is used as the vapor in commercial absorption cycle systems, and water or lithium bromide is the absorber

Absorption Cooling

A process in which cooling of an interior space is accomplished by the evaporation of a volatile fluid, which is then absorbed in a strong solution, then desorbed under pressure by a heat source, and then recondensed at a temperature high enough that the heat of condensation can be rejected to a exterior space

Absorption Chiller

A type of air cooling device that uses absorption cooling to cool interior spaces


Without loss or gain of heat to a system. An adiabatic change is a change in volume and pressure of a parcel of gas without an exchange of heat between the parcel and its surroundings. In reference to a steam turbine, the adiabatic efficiency is the ratio of the work done per pound of steam, to the heat energy released and theoretically capable of transformation into mechanical work during the adiabatic expansion of a unit weight of steam.

Active Solar Heater

A solar water or space-heating system that use pumps or fans to circulate the fluid (water or heat-transfer fluid like diluted antifreeze) from the solar collectors to a storage tank subsystem


A component of a heat pump that stores liquid and keeps it from flooding the compressor. The accumulator takes the strain off the compressor and improves the reliability of the system

Array (Solar)

Any number of solar photovoltaic modules or solar thermal collectors or reflectors connected together to provide electrical or thermal energy


Referring to alterations in the environment due to the presence or activities of humans.

Annual Load Fraction

That fraction of annual energy demand supplied by a solar system

Angle of Inclination

In reference to solar energy systems, the angle that a solar collector is positioned above horizontal

Audit (Energy)

The process of determining energy consumption, by various techniques, of a building or facility


Describes the reliability of power plants. It refers to the number of hours that a power plant is available to produce power divided by the total hours in a set time period, usually a year.

Average Wind Speed (or Velocity)

The mean wind speed over a specified period of time

Azimuth (Solar)

The angle between true south and the point on the horizon directly below the sun.

Apparent Power (kVA)

This is the voltage-ampere requirement of a device designed to convert electric energy to a non-electrical form.



 Refers to the science of soil management, land cultivation and crop production. It is a part of agricultural science that mainly deals with the principles of crop production, soil and water conservation techniques, etc.



Soil or sediments deposited by a river or other running water.


 Small to medium-sized hawks, of the genus Accipiter, characterized by short-broad wings and a long tail, i.e., Cooper's Hawk





 A vertebrate whose skull contains no side openings behind the eyes. The only living examples are turtles.

Acid Fallout

Molecules of acid formed from reactions high in the atmosphere involving nitrogen, sulfur oxides, and water vapor that settle out of the atmosphere without any additional water.


 Rock which has not been moved from its original site of formation


 An antiviral drug.

Abiotic factors

 Environmental influences produced other than by living organisms; for example, temperature, wind patterns, humidity, pH, substrate rock type, and other physical and chemical influences.

Age structure

Age structure is the number of individuals of each age within the population.

animal community

Animals of various species living within a certain habitat, each occupying a specific     position in that particular environment; directly parallel to plant communities.

annual turnover

The rate of replacement of individual animals in a population. Birds, such as quail, may have a 70 percent turnover annually. This means that only 30 percent of the birds alive at the beginning of one year are still alive at the end of the year. The reproductive capabilities of a species will match the mortality, or turnover rate.


Growing, living in, or frequenting waters.

Alpine Zone

Alpine Zone. The altitude above which trees no longer grow varies with altitude, aspect, slope, and other factors, but is generally above 3600m in the western Himalaya.


 A chain or cluster of islands


 Soft-bodied insects that eat green leaves.

adapted, adaptation

 The process of making adjustments to the environment. For example, plants grow only where soil types, moisture, and sunlight are balanced to the proper degree. Desert plants have adapted so they live under intense sunlight, on poor quality soils, and with a much reduced water supply.


 Sensitivity to or appreciation of beauty through recognition of its unique and varied components or through its orderly appearance.

Age Gradation

 An age class with one year as the interval. Loosely used sometimes as synonymous with age class.

Age Class

 One of the intervals into which the range of age of trees growing in a forest is divided for classification or use; also the trees falling into such an interval

Age Classification

 The division of a crop according to differences in age; or the allotment of woods to age classes.


 An effect whereby one plant chemically discourages growth of others in its environment, example by toxins contained in fallen leaves or chemicals released by plant roots.