# Compressional Modulus

From Soft-Matter

The **compressional modulus**, **K**, gives the relation between a change in shear stress, <math>d\sigma</math>, and the relative change in volume, <math>\frac{dV}{V}</math>, for a perfectly elastic material. We define **K** such that:

<math>d\sigma = -K\frac{dV}{V}</math>.

Note that this is for the situation where all sides are compressed due to an equally distributed shear stress; thus, the volume changes but the shape stays the same.

## Reference

[1] W. Norde, "Colloids and Interfaces in Life Sciences," Marcel Dekker, Inc. (2005).