degrees  of  freedom    The  number of independent modes of the system,  by which  the  system  can absorb energy. Consider for example  an  one  dimensional simple  harmonic  oscillator. Its degrees  of  freedom are two, because it has two modes of energy absorption,  the  kinetic  energy  and  the  potential energy. A system  containing  n non-interacting gas molecules has 3n as its degrees  of freedom.  This  is  because each molecule has three independent directions of translation.