Note: Latin difficultās presumably goes back to *dis-fakli-tāts and follows the same path as the base word, from *faklitāts to attested facultās (see faculty), with regular vowel weakening in a non-initial syllable. The word difficilis is derivationally peculiar, as the prefix dis- is regularly applied only to verbs and is not primarily privative—the expected negative counterpart to facilis should have been *infacilis. It has been hypothesized that dis- in this case is a permutation of *dus-, corresponding to Greek dys- "bad, ill" (see dys-; *dus- is otherwise unattested in Latin), or that difficilis is modeled on dissimilis "unlike" (see dissimilar; the adjective similis "like" takes a range of ordinarily verbal prefixes, perhaps following Greek equivalents). Neither solution is entirely satisfactory.