# stress

Stress is force per unit area. If σ is the stress, *F* the force, and *A* the cross-sectional area, then σ = *F*/*A*. **Tensile stress** and **compressive stress** are axial forces applied to a body that tend either to extend it or compress
it linearly. **Shearing stress** is a tangential force per
unit area that tends to shear a body. See also Hooke's
law.

In a fluid, no shearing stress is possible because the fluid slips sideways, so all fluid stresses are pressures (positive or negative).