I was listening to a record at our university about friction and its rheological definition. For the first moment I thought that its the normal definition
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
However the lecture pointed out that the rheological definition is different from the normal one. The professor who recorded the lecture is out of town now so I can't ask him.
So I just need to know any idea what is meant by the Rheological definition of Friction and what makes it different from the normal one??
Any help is appreciated