A thermodynamic cycle is a series of processes that involve the transfer of energy and matter, returning a system to its initial state. These cycles are fundamental in understanding how engines and refrigerators operate, as they describe how energy is converted from one form to another, often involving heat and work. Common examples of thermodynamic cycles include the Carnot cycle, Otto cycle, and Rankine cycle. Each cycle has distinct processes, such as compression, heating, expansion, and cooling, which help in analyzing the efficiency and performance of thermal systems in various applications, including power generation and refrigeration.