Frequency may refer to any of the following:
1. In general, frequency is a measurement of how often something happens in a period of time. In science and technology, frequency is measured in Hz (hertz).
3. A frequency is the number of oscillations in alternating electrical current each second.
4. The term frequency may also refer to cycles per second of an electromagnetic wave, such as a sound wave or a light wave. The frequency of light determines its color, as seen by the human eye. Similarly, the frequency of sound determines its pitch, as heard by the human ear.