Pahlavi is a particular, exclusively written form of various Middle Iranian languages, derived from the Aramaic script. It features Aramaic words used as heterograms (called uzwārišn, "archaisms").
Pahlavi compositions have been found for the dialects/ethnolects of Parthia, Persis, Sogdiana, Scythia, and Khotan. Independent of the variant for which the Pahlavi system was used, the written form of that language only qualifies as Pahlavi when it is both Aramaic-derived and features uzwārišn.
Pahlavi is then an admixture of:
- written Imperial Aramaic, from which Pahlavi derives its script, logograms, and some of its vocabulary.
- spoken Middle Iranian, from which Pahlavi derives its terminations, symbol rules, and most of its vocabulary.
Pahlavi may thus be defined as a system of writing applied to (but not unique for) a specific language group, but with critical features alien to that language group. It has the characteristics of a distinct language, but is not one. It is an exclusively written system, but much Pahlavi literature remains essentially an oral literature committed to writing and so retains many of the characteristics of oral composition.
Work in progress...