The Pascal-second is a unit of dynamic viscosity in the International System of Units (SI). It measures a fluid's resistance to flow, indicating how thick or thin a liquid is. A higher value means the fluid is more viscous, while a lower value indicates it flows more easily. One Pascal-second is defined as the viscosity of a fluid that requires a force of one Pascal to move one square meter of the fluid at a rate of one meter per second. This unit is commonly used in various fields, including engineering and physics, to analyze fluid behavior.