1, different definitions: Stickiness means that sticky things are connected or attached to other objects; Stickiness refers to the property that one object adheres to another.

2. Essentially different: viscosity is the characteristic of some solids formed by molecular force (also called van der Waals force) between their internal molecules; Viscosity is the adsorption property of fluids (such as oil, water, ink, etc.). When they are under pressure or encounter different surfaces.