A combined study of vibrational and thermodynamic properties of metaboric acid (BOH)(3)O-3 crystal polymorphs alpha, beta, and gamma were obtained through density functional theory (DFT) calculations in an attempt to resolve the conflicting assignments that currently exist in the literature for them. A complete correlation between the normal-mode assignment and vibrational signatures to distinguish particular features of each metaboric acid polymorph, in particular, those related to motions of the planar layers in alpha-(BOH)(3)O-3, with a level of detail surpassing essays based on previous published experimental works has been achieved. Besides, no DFTbased research work was published early on the (BOH)(3)O-3 polymorph vibrational properties, and our DFT-simulated infrared and Raman spectra for all metaboric acid polymorphs agree very well with experiment. Comparison of the previously published experimental IR and Raman spectroscopic results with predictions from higher levels DFT calculations allows identification of the in-plane and out-of-plane B-O bending modes. For example, the strongest measured (DFT-calculated) Raman modes of alpha-(BOH)(3)O-3 at 591 and 797 cm(-1) (599 and 810 cm(-1)) are identified as vibrational signatures of breathing B3O3/Ag in-plane modes, while the shoulder in the lattice modes region at 135 (143) cm(-1) is the vibrational signature of the bending B3O3/B-1g out-of-plane mode. Phonon-dispersion bands and their respective phonon densities of states were also evaluated for each system, as well as temperature-dependent curves for entropy, enthalpy, free energy, heat capacity, and Debye temperature. Phonon dispersion curves are singular for each (BOH)(3)O-3 species, and a consistent gap decrease between the lowest and highest frequency vibrational bands was observed. The DFT-based calculations also revealed that the noncovalent interactions prevalent in the alpha and beta crystals lead to significant differences with respect to the thermodynamic properties in comparison with the gamma phase.