  This study provides a new interpretation of 3D particle geometry that
unravels the 'interrelation' of the four geometry parameters, i.e., morphology
M, surface area A, volume V, and size L, for which a new formula, M =
A/V$\times$L/6, is introduced to translate the 3D particle morphology as a
function of surface area, volume, and size. The A/V$\times$L of a sphere is
invariably 6, which is placed in the denominator of the formula, and therefore
M indicates a relative morphological irregularity compared to the sphere. The
minimum possible value of M is clearly one, and M may range approximately to
three for coarse-grained mineral particles. Furthermore, the proposed formula,
M = A/V$\times$L/6, enables to graphically preserve the four parameters'
relations when plotting the geometry parameter distributions. This study
demonstrates the approach with two plot spaces that represent (i) L vs. M and
(ii) A/V vs. V, where A/V works as the messenger between these two spaces as
A/V = M/L$\times$6. Therefore, this approach helps comprehensively address the
four-dimensional aspects of the 3D particle geometry and better understand the
parameters' combined influence on the mechanical behavior of granular
materials.
  Keywords: 3D particle geometry; Morphology; Surface area; Volume; Size;
