Subject: What does the abbreviation Rf mean?

The Science teacher and I have been trying to find out what "Rf" 
(f is
written as a subscript) stands for. It was used in an equation 
that she
found in an experiment that shows the separation of components of
lipstick. The equation is:
Rf = distance component travel / distance solvent traveled

She knows her class will ask "What does Rf mean?" We can't find 
it in
any science symbols tables. Please help!

Thank you
Mrs. Martha Griffin
Technology Coordinator
St. Paul School
Burlington, NJ

Re: What does the abbreviation Rf mean?