This article argues that Differential Argument Indexing (DOI) and Differential Argument
Marking (DOM) constructions in Coptic (Afroasiatic, Egypt) are reanalyzed, resulting in
a set of verbs with interposed P-indexes within bipartite stems (DeLancey 1996; Nichols
2003). Basically, incorporated noun phrases with prefixed possessor indexes become parts
of derived verbs with unpredictable lexical semantics, and their erstwhile possessor prefixes,
entrapped within the derived verb, are reanalyzed as P-interpositions. Since this possessor
prefix ultimately developed from an earlier possessor suffix, the pathway documented here,
stripped down to its essentials, is suffix → prefix → interposition, and erstwhile com-
plex construction → bipartite stem. Finally, an overt genitive prefix that marks lexical
possessors of incorporated noun phrases is reanalyzed as an accusative case prefix. These
changes introduce new complexity into Coptic Differential Argument Marking: not only
are P arguments either indexed as suffixes, case marked, or incorporated for the majority of
verbs, they can be indexed as interpositions for a lexically determined set of verbs.