The unafical definition of filk that I've accepted is that it's music written in the stile of folk music, but is not exactly folk eather because of the subject, i.e. sci-fi fantacy, or modern subjects such as computers, or scadian, or it's not folk because it's a modification, paridy, pariphrase, or borows the melody of a folk song, or by some wim has gotten lumped in with filk music. determining weather it's folk or filk is not a very precise business.