Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation.

A process whereby oil is recovered other than by the natural pressure in a reservoir.

Enhanced geothermal systems (EGS) actively inject water into wells to be heated and pumped back out. The water is injected under high pressure to expand existing rock fissures to enable the water to freely flow in and out.

Engineering tolerance is the permissible limit or limits of variation.

Engineering fits are generally used as part of geometric dimensioning and tolerancing when a part or assembly is designed.

An engineering drawing is a type of technical drawing that is used to convey information about an object.

Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings.

An engine preheater is the device that preheats the engine at low temperatures before starting. It protects and warms up the engine by heating up the coolant and transferring the heat to the engine through the coolant.

When spark ignited combustion is not complete for the fuel/air mixture in a cylinder, unburnt mixture "explodes" due to compression creating a knokinging of pinging noise.

An engine control unit (ECU), also commonly called an engine control module (ECM) is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance.

A machine that converts one form of energy into another. A combustion engine connected to an electrical motor can produce electrical energy.

In open channel flow, specific energy (e) is the energy length, or head, relative to the channel bottom.

An energy-plus building produces more energy from renewable energy sources, over the course of a year, than it imports from external sources.

Fly ash or flue ash is a coal combustion product that is composed of the particulates (fine particles of burned fuel) that are driven out of coal-fired boilers together with the flue gases.

Velocity of fluid (often stated in feet/second) required to force air out of any pipe in a ground loop heat exchanger, generally accepted minimum is 2 feet/sec.

A gasifier whereby the fuel is fluidized in oxygen and steam or air.

Fluidization is a process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state.

Fluidics, or fluidic logic, is the use of a fluid to perform analog or digital operations similar to those performed with electronics.

Fluid pressure is most often the compressive stress at some point within a fluid.

Fluid mechanics is the branch of physics concerned with the mechanics of fluids (liquids, gases, and plasmas) and the forces on them.