An atom is the smallest unit of ordinary matter that forms a chemical element.

The reduction in the transparency of air resulting both from the scattering of light by tiny particles suspended in the air (water droplets, ice crystallites, and dust and smoke particles) and from the absorption of light by water vapor.

Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth.

The mass per unit volume of the earths atmosphere, used in calculations when investigating and planning wind farms.

ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, and services.

Associated petroleum gas, or associated gas, is a form of natural gas which is found with deposits of petroleum, either dissolved in the oil or as a free "gas cap" above the oil in the reservoir.

The person or company that has ownership or responsibility for property or machinery.

A data set from the analysis of operational data sets usually for trouble shooting or system improvements.

Property or machinery, that has value to a company or individual.

Asphalt, also known as bitumen, is a sticky, black, highly viscous liquid or semi-solid form of petroleum.

The BPVC provides rules for the design, fabrication, installation, inspection, care, and use of boilers, pressure vessels, and nuclear components.

The American Society of Mechanical Engineers

Ashden is a London-based charity that works in the field of sustainable energy and development.

An ash pond, also called a coal ash basin or surface impoundment, is an engineered structure used at fossil fuel power stations for the disposal of two types of coal combustion products: bottom ash and fly ash.

A detailed drawing that shows everything included on the site plan in addition to the exact location, dimensions, and other pertinent details for a given GHEX installation after the installation is complete.

Artificiality (the state of being artificial or human-made) is the state of being the product of intentional human manufacture rather than occurring naturally through processes not involving or requiring human activity.

A human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, offshore wind farms are contributing to the creation of artificial reefs.

Artificial intelligence is intelligence demonstrated by machines, unlike the natural intelligence displayed by humans and animals, which involves consciousness and emotionality.

Aromatic compounds are those chemical compounds (most commonly organic) that contain one or more rings with pi electrons delocalized all the way around them.

In electrical power distribution, armoured cable usually means steel wire armoured cable (SWA) which is a hard-wearing power cable designed for the supply of mains electricity.