Mohr’s circle shows that description depends on viewpoint without making the underlying reality subjective.

Mohr’s circle is a graphical method for representing and analyzing stresses or strains at a point within a material. The circle transforms the normal and shear components acting on different planes into points on a two-dimensional graph. By examining the circle, engineers can determine principal stresses, maximum shear stress, principal directions, and the stresses acting on any rotated plane. The center and radius of the circle summarize the stress state and make otherwise complicated transformation equations visually intuitive. Named after German engineer Otto Mohr, the construction is a standard tool in mechanics of materials. It is used in structural engineering, mechanical engineering, and stress analysis.