A body at temperature absolute zero is the coldest possible; the thermal motion of all its fundamental particles is minimum. Although classically described as motionless at the absolute zero of temperature, particles still possess a finite zero-point energy in the quantum mechanical description. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, and −459.67 °F on the Fahrenheit scale.
Temperature is a proportional measure of the average kinetic energy of the random motions of the constituent microscopic particles in a system (such as electrons, atoms, and molecules); based on the historical development of the kinetic theory of gases, but more rigorous definitions include all quantum states of matter.
Many physical processes are affected by temperature, such as
Temperature scales differ in two ways: the point chosen as zero degrees, and the magnitudes of incremental units or degrees on the scale.