Technically a thermodynamic quantity, in gases it is the product of pressure and adiabatic index and in fluids, density and this quantity determine the speed of sound.
For crystalline solids with less than cubic symmetry, this quantity is not uniform in all directions and must be replaced with a tensor with more than one independent variable for proper description. Technically a thermodynamic quantity, in gases it is the product of pressure and adiabatic index and in fluids, density and this quantity determine the speed of sound. Unlike the shear type, this quantity describes the material's response to uniform compression, so its inverse is compressibility. For 10 points, name this elastic modulus, defined as the pressure necessary to produce a given relative decrease in volume, which is notably not Young's.
For crystalline solids with less than cubic symmetry, this quantity is not uniform in all directions and must be replaced with a tensor with more than one independent variable for proper description.
{bulk modulus} (only need "bulk" after modulus given)