Temperature is the measure of the mean kinetic energy of the molecules of an object. It is a physical quantity that determines the direction of heat flow between two objects in contact. The higher the temperature of an object, the higher the mean kinetic energy of its molecules and the greater its capacity to transfer heat to other objects. Conversely, a lower temperature corresponds to a lower mean kinetic energy and a lower capacity to transfer heat. Temperature is usually measured in degrees Celsius (°C) or Fahrenheit (°F), or in kelvin (K) in the international system of units.