Old Persian is, besides Avestan, the oldest attested Old Iranian language. It is a member of the Southwestern Iranian group of Indo-Iranian languages, belonging to the Indo-European language family. It is attested between 521 – 338 BC, dating to the reign of the king Darius, Xerxes and Artaxerxes.
Sources for Old Persian are very limited. We are left mostly with inscriptions carved in stone found in Persis, Media, Armenia and along Suez Canal. These can be dated from the reign of the Achaemenid royal dynasty, the first written by Darius the Great and the last by Artaxerxes the III (521 – 338 BC). Besides the inscriptions on stone, several are found on metal and limited number of clay tablets. Many of them are trilingual (Old Persian accompanied by Babylonian and Elamite). An important source are as well OP words preserved in other languages, mainly Hebrew, Lydian, Lycian, Egyptian, Greek, Latin and early Middle Indic texts.
Old Persian is an inflectional, synthetic language, where most morphological information is captured by the word ending. The basic words order is SOV; the final verb can be seen in all given examples (except 1.1.1a, where there is no verb).
The Old Persian corpus is restricted mainly to several inscriptions carved in stone, besides short inscriptions on vases, seals etc. Examples of adjective valence are therefore scarce. The inscription texts are often repetitive, with set formulas, and do not provide much variety of syntactic style.
However, the number of examples is not scarce in relative terms – as to the amount of the preserved data and adjective valence examples, adjective valence plays an important role in Old Persian syntax.
Bibliography:
Brandenstein W. 1964. Handbuch des Altpersischen. Wiesbaden: O. Harrassowitz.
Kent R.G. 1953. Old Persian. Grammar, texts, lexicon. New Haven, Connecticut: American Oriental Society.
Schmidt R. 1989. Altpersisch. In: R. Schmitt, Compendium linguarum Iranicarum. Wiesbaden: Reichert, p. 56–85.
Schmidt, R. 2008. Old Persian. In: Woodard R. D. (ed.), The Ancient Languages of Asia and the Americas. Cambridge: Cambridge University Press, p. 76-100.