Friction loss refers to the reduction in pressure that occurs when a fluid flows through a pipe or duct. This loss is caused by the friction between the fluid and the walls of the pipe, as well as the interactions between the fluid molecules themselves. The longer and narrower the pipe, the greater the friction loss, which can affect the efficiency of fluid transport systems. In practical applications, such as in firefighting or plumbing, understanding friction loss is crucial for ensuring adequate water pressure and flow rates. Engineers often use specific formulas and charts to calculate friction loss, allowing them to design systems that minimize pressure drops and optimize performance.