P1 = initial absolute pressure
P2 = final absolute pressure
V1 = initial volume
 V2 = final volume
T1 = initial absolute temperature
T2 = final absolute temperature

generator (electrical machine). A device that converts mechanical energy into electrical energy by rotating coils of wire through a magnetic field. As the conductors in the coils cut across the lines of magnetic flux, a voltage is generated that causes current to flow.
generator field (A-circuit). A generator circuit in which the voltage regulator is installed between the shunt field and ground.

generator field (B-circuit). A generator circuit in which the voltage regulator is installed between the shunt field and the armature.

generator series field. A set of heavy field windings in a generator connected in series with the armature. The magnetic field produced by the series windings is used to change the characteristics of the generator.
generator shunt field. A set of field windings in a generator connected in parallel with the armature. Varying the amount of current flowing in the shunt field windings controls the voltage output of the generator.
geodetic construction (aircraft structure). A form of stressed skin construction in which the stresses are carried in a portion of the structure made up of strips of metal or wood that cross to form a diamond-shaped lattice. Geodetic structure was used for aircraft construction in the past, but has been replaced to a great extent by monocoque structure, which is similar to geodetic except it uses solid sheets of thin metal, rather than the lattice structure.
GEO map (air traffic control). The digitized map markings associated with the ASR-9 radar system.
geometric pitch (aircraft propeller specification). The distance a propeller would advance in one revolution if it were turning in a solid. The geometric pitch of a propeller does not take slip into consideration.
geopotential of the tropopause. The point in the standard atmosphere where the temperature stops dropping and becomes constant. This is the tropopause, or the dividing line between the troposphere and the stratosphere.
germanium. A brittle, crystalline, gray-white, metallic chemical element. Germanium’s symbol is Ge, its atomic number is 32, and its atomic weight is 72.59. Germanium is in the same chemical family as carbon, silicon, tin, and lead, and is obtained from the residue left when lead and zinc are refined electrolytically. Germanium is widely used in the manufacture of semiconductor devices.
German silver. An alloy of copper, zinc, and nickel. German silver is also called nickel silver.
gerotor pump (fluid pump). A form of constant displacement gear pump that uses an external-tooth drive gear that meshes with and drives an internal-tooth gear that has one more space for a tooth than there are teeth on the drive gear. Both gears turn inside a close-tolerance housing.