👉 Hertz is a unit of measurement used to express the frequency of oscillations in a physical system. It is named after the German physicist Heinrich Hertz, who first defined it as the number of cycles per second (Hz) for the electromagnetic wave that he discovered in 1896. In physics and engineering, hertz is often used to measure the speed of light or other waves such as sound, water waves, and seismic waves. It is also used in many areas of science