From small strain, the ratio of longitudinal stress to corresponding longitudinal strain is defined as the Young's modulus (V) of the body.
In response to hydrostatic load, the specimen will change its volume, its resistance to do so i0 quantified as bulk modulus K, whereas ratio of shear stress to the shear strain is defined as shear modulus (η).
The relation between the three is given by Y9=K1+η3