Hertz (Hz) is a unit of frequency that measures the number of cycles per second of a periodic phenomenon. It is commonly used in various fields, including physics, engineering, and audio technology. For example, a sound wave with a frequency of 440 Hz corresponds to the musical note A above middle C, which is widely used as a tuning standard. In addition to sound, Hz is also applicable in other contexts, such as electromagnetic waves, where radio frequencies are measured in kilohertz (kHz), megahertz (MHz), and gigahertz (GHz). Understanding Hz is essential for grasping concepts related to waves, signals, and oscillations in both natural and technological systems.