Rain that has become acidic due to the emission of sulfur dioxide and nitrogen oxides.

The air leakage rating is a measure of how much air leaks through the crack between the window sash and frame. The rating reflects the leakage from a window exposed to a 25-mile-per-hour wind, and is measured in cubic feet per minute per linear foot of sash crack.

Electric current which changes direction with a regular frequency. Domestic mains in the UK have a frequency of 50 Hertz.

An electric generator designed to produce alternating current. Usually consists of rotating parts which created the changing magnetic field to produce the alternating current.

The surrounding temperature of an area.

A standard measure which represents the size of wire. The larger the number, the smaller the wire. Abbreviated AWG.

The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

A type of electric current produced by one volt applied across a resistance of one ohm. It is also equal to the flow of one coulomb per second.   Named after French physicist Andre M. Ampère 1836.

A measuring or display methodology which uses continuously varying physical parameters. In contrast, digital represents information in discrete binary form using only zeros and ones.

An indication of how well a furnace converts energy into usable heat. The rating is expressed as a percentage of the annual output of heat to the annual energy input to the furnace.

Utilization equipment, generally other than industrial, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, etc.