The unitless number you're describing is actually called the coefficient of friction. Here's why:

* Friction is a force that opposes motion between two surfaces in contact. It is measured in Newtons (N).

* Weight is the force of gravity acting on an object, also measured in Newtons (N).

* Coefficient of friction is a dimensionless quantity representing the ratio of the frictional force to the normal force between two surfaces. It's a measure of how "sticky" or "rough" the surfaces are.

Therefore, the correct statement is:

The amount of friction divided by the normal force (which is often equal to the weight of the object on a horizontal surface) forms a unitless number called the coefficient of friction.