Which measurement indicates how much a liquid will resist flow?

The measurement that indicates how much a liquid will resist flow is viscosity. Viscosity is a property of fluids that describes their internal resistance to flow; thus, it determines how easily a liquid can move. A liquid with high viscosity, such as honey or glycerin, flows more slowly than a liquid with low viscosity, like water or alcohol. This concept is crucial in various applications, such as in mechanical systems, where the viscosity of the hydraulic fluid can significantly affect performance and efficiency.

Density, on the other hand, refers to the mass of a substance per unit volume, providing insight into how heavy a liquid is relative to its size, but does not directly relate to its flow characteristics. Specific gravity is a dimensionless quantity that compares the density of a liquid to the density of water, which again does not measure how resistant to flow a liquid is. Pressure describes the force exerted by a fluid per unit area, but it also does not indicate the flow resistance within the liquid itself. Therefore, viscosity is the accurate measure of a liquid's resistance to flow.