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Watt (W)
The unit of power in the metric system. The watt describes how fast a circuit uses electrical energy.

Wattmeter
Also called a power meter, a test instrument used to measure the power output (in watts) of a transmitter. A directional wattmeter measures both forward and reflected power.

Wavelength
Often abbreviated ?. The distance a radio wave travels in one RF cycle. The wavelength relates to frequency. Higher frequencies have shorter wavelengths.

X
In electrical equations, this letter stands for "Reactance."