 Thus, the meaning of any such word is often difficult to determine, because cross-references and comparisons with other usages are not possible, except by morphological analysis.The most popular morphological analysis sees prefix "epi-" and a polysemantic word "ousia" even though that doesn't follow the standard Greek form of building compound words.Usually the iota at the end of "epi" would be dropped in the compound (compare, e. g., eponym).