A kilohertz (kHz) is a unit of frequency equal to one thousand cycles per second. Hertz measure cycles per second, and kilo means one thousand. Thus five-kilohertz is five thousand cycles per second. kHz is most commonly used in reference to radio frequencies and audio signal processing. These measurements in audio most frequently pertain to the audio spectrum (audible from around 20 Hz to 20 kHz), although hertz is a generic term, which may be applied to any analog waveform be it electrical, audio, visual, wireless signals, or other.