# Degree of freedom

In classical mechanics, a **degree of freedom** is each of the *generalized* coordinates that specify a given configuration of a system. For example, a position in space is specified by three numbers (e.g. the Cartesion coordinates), hence three degrees of freedom are needed for translation. An orientation would be specified by two
numbers (e.g. the Eulerian angles).

Often, *effective* degrees of freedom must be considered. For example, diatomic molecules would need 6 degrees of freedom, 3 for each atom (since these two can be anywhere in the system). However, vibrations are *frozen* at temperatures below thousands of K, and only 5 effective degrees of freedom are needed. E.g.: three to specify the location of the centre-of-mass, and two angles to specify rotation. (Rotations may also be *frozen*, but this happens at low temperatures.)