In linear elasticity, the P-wave modulusM, also known as the longitudinal modulus, is one of the elastic moduli available to describe isotropic homogeneous materials.
It is defined as the ratio of axial stress to axial strain in a uniaxial strain state
Homogeneous isotropic linear elastic materials have their elastic properties uniquely determined by any two moduli among these, thus given any two, any other of the elastic moduli can be calculated according to these formulas.