A molecule with n atoms that is rigid and not linear has 3 translation modes and 3 non-trivial rotation modes, hence only 3 n − 6 deformation modes. It therefore has f = 3 + 3 + 2(3 n − 6) = 6 n − 6 energy-absorbing degrees of freedom (one less than a linear molecule with the same atom count). Water H 2 O (n = 3) is bent in its non-strained state, therefore it is predicted to have f = 12 degrees of freedom. Methane CH 4 (n = 5) is tridimensional, and the formula predicts f = 24.