The natural temperature of the earth in a specific location.

The surrounding air (usually outdoor air or the air in a specific location).

Natural condition of the environment at any given time.

ACCC (Aluminum Conductor Composite Core) is a registered trade mark for a type of "high-temperature low-sag" (HTLS) overhead power line conductor.

Aluminium conductor steel-reinforced cable (ACSR) is a type of high-capacity, high-strength stranded conductor typically used in overhead power lines.

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current.

Electrical current that flows is bi directional.

Alpine climate is the typical weather (climate) for the regions above the tree line.

Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus.

Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two.

An alloy is an admixture of metals, or a metal combined with one or more other elements.

Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.

A battery electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, with no secondary source of propulsion.

In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins.

In chemistry, an alkene is a hydrocarbon that contains a carbon–carbon double bond.

One of the most developed fuel cell technologies.

A type of primary battery which derives its energy from the reaction between zinc metal and manganese dioxide.

Algae fuel, algal biofuel, or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils.

Albedo is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that reflects all incident radiation.

ALARP ("as low as reasonably practicable"), or ALARA ("as low as reasonably achievable"), is a principle in the regulation and management of safety-critical and safety-involved systems.