# Why isn't there a “parallel” Pressure as there is a parallel or shear Stress?

I had this question while I was reading the differences between pressure and stress.

Pressure is the intensity of external forces acting on a point, and it always act normal to the surface.

Stress is the intensity of internal resistance force developed at a point, and it could be either normal or parallel.

Ok then, why isn't there a parallel or a shear pressure?

When I thought about an answer, I told myself, by referring to its definition, that it may be because it is acting on a point, so if there is a parallel pressure then it won't be acting on a point but instead it will be acting on a surface. Great then let us do another definition for a parallel pressure.

But then shear stress is acting on a surface and not on a point, so how come that stress is defined to be acting on a point while shear stress opposes this idea?

• Seems odd that you're trying to force an isomorphism. It's tempting, but pressure is always normal. Pressure is a type of stress in a solid (normal type), shear is the parallel type. They're not analagous, pressure is a subset of a type of stress in solids. You can also have shear and pressure in gases and liquids too though obv. – AER Jun 17 '20 at 23:45