Viscosity is a parameter used to measure the consistency of liquid materials, indicating whether they are thin or thick. It refers to the resistance to flow that occurs when molecules slide within the liquid. In simpler terms, viscosity quantifies the fluid's resistance to flow. Commonly used units for measuring viscosity are centipoise (cps) and millipascal-second (mPa.s). Essentially, higher viscosity denotes a more viscous and resistant-to-flow liquid, while lower viscosity indicates easier fluidity.