The temperature is a quantity referred to the common notions of hot, warm, cold can be measured, specifically, with a thermometer. In physics, is defined as a scalar quantity related to the internal energy of a thermodynamic system defined by the zeroth law of thermodynamics. More specifically, it is related directly to the internal energy known as "kinetic energy" is the energy associated with the motion of particles in the system, either in a sense translational, rotational, or in the form of vibrations. As is greater than the kinetic energy of a system, it is observed that is more "hot", ie, its temperature is increased.
The temperature is measured with temperature sensors, which can be calibrated according to a multitude of scales resulting in units of temperature measurement. In the International System of Units, the unit of temperature is the kelvin (K), and the corresponding scale is Kelvin scale or an absolute scale, which associates the value «zero kelvin» (0 K) at 'absolute zero', and graduated with a size equal to the Celsius degree. However, outside of the scientific use of other common temperature scales. The most widely used scale is the Celsius scale, called "centigrade", and to a much lesser extent, and almost exclusively in the United States, the Fahrenheit scale. It is also sometimes used the Rankine scale (° R) established its benchmark in the same point of the Kelvin scale, absolute zero, but with a size equal to the Fahrenheit degree, and is used only in the U.S. , and only in some engineering fields.