Betz limit: The theoretical upper limit to wind power's capacity factor, that is to the percent of available energy that a wind turbine can actually capture as usable energy.

Capacity Factor: The percent of theoretically available energy that is actually converted to usable energy; a percentage comparing a "plant's actual production over a given period of time with the amount of power the plant would have produced if it had run at full capacity for the same amount of time" (AWEA FAQs 5).

Don Quixote: The hero of a 1605 novel by the same name by Miguel de Cervantes Saavedra, considered the predecessor of the modern novel. Don Quixote attempted to return to the grand days of yore, setting himself as a knight errant and embarking on comic misadventures. In one of these, he attacked a group of windmills, mistaking them for giants.

Grid or Electrical Grid: The network of generators and power lines in a region. Due to intermittency, wind turbines work best in conjunction with other power sources on the grid.

Intermittency: The tendency to stop, start, and vary in strength that makes wind power unpredictable. Wind power must therefore either work in conjunction with other energy sources or else be stored for use during slow (or no) wind periods.

Kilowatt-hour: A unit of energy equivalent to the work done by one kilowatt (1 kW) of power expended for one hour. This is more formally expressed in joules: one Kilowatt-hour equals 3,600 joules.

Kinetic Energy: Energy of motion. Once a body takes on this energy it maintains it unless its speed changes. Energy can never be destroyed but can be converted to other forms; wind power converts kinetic energy of wind to mechanical energy from rotating shafts and then into electrical energy.

Nacelle: In a wind turbine, "the frame and housing at the top of the tower. It protects the gearbox and the generator from weather, and helps control the mechanical noise level."

NIMBY: Acronym for "Not In My Back Yard," a term used, often derisively, for individuals or communities who work to block projects, often with a wider public use, in their neighborhoods, believing that they will lower the area's attractiveness, safety, and/or financial value. Incinerators, homeless shelters, and rail projects are common causes of NIMBY opposition.

Peak Availability: The peak availability of a product after which supplies slowly dwindle and price tends to rise. "Peak Oil" is a commonly used term for the point at which half of global oil reserves have been used. When this will happen, or even if it might already have occurred, is not known.

Shadow Flicker: The flickering caused by the blades of a wind turbine, which can be disconcerting.

Tower: "A steel structure, typically tubular, with a ladder up the inside for maintenance access."

Transduction: Transference or conversion of one type of energy to another; also refers to transference of genetic material.

Turbine: "A device that converts the kinetic energy of a moving fluid into rotational energy . . . . A wind turbine's blades use aerodynamic lift and drag to capture some of the wind's energy and turn the generator's shaft." Today's wind turbines commonly have three blades.

Yaw: "Commercial-scale turbines have a motor to yaw, or turn the rotor to face into the wind. At high wind-speeds, they yaw out of the wind to protect themselves."

Source for quotations in glossary: University of Massachusetts at Amherst, Renewable Energy Research Laboratory. The Power & Capacity of Wind.