Can some one please explain what exactly is pressure ??? From thermodynamics point of view, it is clear. But how can we define pressure from Hydrodynamics point of view and we have learnt that as velocity increases pressure decreases according to Bernoulli's principle ( for straight stream lined flow). What is this pressure ?? It's also clear to me that Pressure is a scalar (it remains same irrespective of angle of orientation of point area on which it's acting) and different from normal stress whis is a tensor. It may sound silly query however, i would like to convince me. Hoping constructive reply. Regards, Murthy

Kinetic theory of gases tells us that it is the momentum exchange between moving molecules as they hit each other or hit a solid boundary.

Yeah! you are true...But how can we extend this Kinetic Theory of gases to liquid...as i said earlier Pressure is a not a thermodynmic property...It's some thing that related flow (Hydrodynamic quantity)..