Final answer:
Hertz (Hz) is a unit of frequency representing the number of cycles per second, applicable to various types of waves, including sound and radio waves.
Step-by-step explanation:
The term Hertz (Hz) is used in physics to describe the frequency of a periodic event, specifically the number of cycles that occur in one second. One hertz is equivalent to one cycle per second. This concept is commonly applied to various types of wave phenomena, such as sound waves, light waves, and radio waves. For example, if you observe 10 wave crests passing a fixed point in one second, the frequency of this wave is 10 Hz. In the context of radio, frequencies are often expressed in kilohertz (kHz), which are thousands of hertz, or megahertz (MHz), which are millions of hertz.