fluidity

Fluidity is the capacity of a substance to flow. In physics, this property is fundamental to understanding fluids, which include liquids and gases. Unlike solids, fluids cannot sustain a shear stress and continuously change shape when subjected to it. This tendency to flow is what defines a fluid.123

Viscosity is a measure of a fluid's resistance to flow. The reciprocal of viscosity is fluidity, indicating how easily a substance flows. Gases tend to expand to fill any available volume, while liquids maintain a definite volume but conform to the shape of their container. There is no fundamental distinction between gases and liquids; they are simply different states of a fluid.456