Dilation, $e$, is a measure of the change in [[Volume|volume]] relative to the object volume, essentially the volumetric equivalent of [[Strain|strain]]. $e=\varepsilon_x+\varepsilon_y+\varepsilon_z$ $e=\dfrac{1−2\nu}{E}(\sigma_x+\sigma_y+\sigma_z)$ Subjecting a material to a hydrostatic (uniform) [[Pressure|pressure]], $P$, results in the following dilation: $e=−\dfrac{3(1−2\nu)}{E}P$ The bulk modulus, $k$, describes how easily a material’s volume will change when subjected to a uniform [[Force|load]]. Bulk modulus is defined by the above-mentioned hydrostatic loading condition. $k=−\dfrac{P}{e_{hydrostatic}}$ $k=\dfrac{-P}{\dfrac{−3(1−2\nu)}{E}P}$ $k=\dfrac{E}{3(1−2\nu)}$