What is the unit of measure for the coefficient of friction?

The coefficient of friction is a ratio that represents the frictional force between two surfaces in contact relative to the normal force pressing them together. Being a ratio of two forces, it is dimensionless, meaning it has no units associated with it. This is because when you divide the force of friction (measured in newtons) by the normal force (also measured in newtons), the units cancel each other out, resulting in a pure number. For example, if the frictional force is 10 newtons and the normal force is 20 newtons, the coefficient of friction would be 10/20, yielding a value of 0.5. Thus, the coefficient itself does not carry any units, indicating the level of friction relative to the forces acting on the surfaces.