Which of the following properly defines viscosity?

Viscosity is defined as the resistance of a fluid to flow. It essentially describes the internal friction within the fluid that arises from the interactions between the molecules as they move past one another. A fluid with high viscosity, like honey, flows more slowly compared to a fluid with low viscosity, like water, which flows more easily. This property is crucial in many applications, including engine oil specifications, where the viscosity of the oil can affect engine performance, fuel efficiency, and wear on engine components. Understanding viscosity helps in selecting the appropriate fluids for various engineering and mechanical systems to ensure optimal performance and reliability.