In the present work authors have developed a simple phenomenological approach to deduce expressions for heat capacity at constant volume CV of linear polymers, considering both inter- and intra-molecular structural characteristic of these materials. The study reveals that correct identification and estimation of both group and skeletal vibrations is essential for the development of the formalism for CV of polymers. Further it is shown that for these materials, heat capacity at constant pressure CP can be obtained through CV using Nernst-Lindemann equation. The computed values of CV and CP of nine polymeric samples viz. crystalline polyethylene (PE), poly (oxymethylene) (POM) and poly (tetrafluoroethylene) (PTFE); and five semi-crystalline chlorine/fluorine containing polymers, poly (vinylfluoride) (PVF), poly(vinylidenefluoride) (PVF2), poly (trifluoro ethylene) (PVF3), poly vinylidene chloride (PVC2) and polychloro-trifluoro-ethylene (PCTFE), and one amorphous poly(vinylchloride) (PVC) in the glassy, leathery and rubbery regions i.e over a wide temperature range (100-400K) are in excellent agreement with the reported data (maximum deviation 5 % for CV and CP values). The developed formalism clearly distinguishes between crystalline, semi-crystalline and amorphous polymers and thus paves a path for better understanding of structure â€“property correlations in polymeric materials.