The Kelvin is a fundamental unit of temperature in the International System of Units (SI), used to measure thermodynamic temperature. It quantifies the absolute temperature of a system, providing a reference point for various scientific and engineering applications. The Kelvin's symbol is K, and it is defined such that 0 K represents absolute zero, the theoretical temperature at which particles have minimal vibrational motion. Unlike Celsius and Fahrenheit scales, the Kelvin scale is an absolute temperature scale, crucial in fields such as physics, chemistry, and engineering. For everyday applications, temperatures in Kelvin are often expressed in relation to the Celsius scale, where 0 °C equals 273.15 K. The Kelvin's importance extends to practical contexts, such as in the measurement of gas temperatures and in scientific research involving cryogenics and high-temperature processes.