The adhesive-cohesive property of a grease, i.e., how well a grease adheres to the surface that it lubricates. In the adhesive industry, tackiness was defined as the force applied to separate two solid surfaces joined by an adhesive layer in its liquid state. In the grease industry, tackiness is qualitatively considered as the ability of a grease to form threads as it is being pulled apart, e.g., when a small amount of grease is held between the thumb and forefinger of an operator, and the operator increases the gap between their thumb and forefinger. Research is underway to develop a formal definition and quantitative test method to measure tackiness and adhesion of grease.