Many people, even clever people, get this wrong. Understanding the meaning of viscosity in reverse.

Viscosity refers to a liquid's resistance to flow (friction). It is usually measured using the Poise scale, named after Frenchman Jean Léonard Marie Poiseuille. The higher the number value then the 'thicker' is the liquid and hence its resistance to flow. Water flows more readily than syrup for example.

Poise is most frequently used with the prefix centi (cP). The viscosity of water at 20°C STP (Standard Temperature and Pressure conditions) is almost exactly 1 centipoise. A centipoise is one hundredth of a Poise, also one millipascal-second (mPa⋅s) in SI units. 1 cP = 10−3 Pa⋅s = 1 mPa⋅s.

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