Historically there are three major periods of development within the Persian language: Old Persian, the language of the Achaemenians (650 – 350 B.C.); Middle Persian (the Parthian period c. 350 B.C. – 230 A.D. and, immediately following that, the Sassanian period c. 230 – 650 A.D.), and New Persian, which starts to take shape after the Iranian conquest by the Arabian armies in the seventh century.
New Persian, in turn, can be divided into two major periods (regardless of the dialectal/regional variations): Classical Persian and Modern Persian. Just where can we draw the line between these two periods is a matter of debate. Probably we never can. What can be suggested with some certainty, however, is that after the invasion of Iran by the Arabian armies—due to the richness of the family of the languages which we commonly know as the “Iranian” languages—it took roughly three hundred years for this new variation of Persian to be developed and used as lingua franca.
To this should be added that since a language is a living entity, it is constantly changing and developing. Within the same generation, probably young members are already speaking somewhat differently than the older ones. This also has to be taken under consideration. In modern times, with increased immigration, globalization and the fusion of cultures, and, more importantly, with the development of the Internet system, a need to communicate differently than the traditional fashion seemed necessary.
The following section details the historical development of the Persian Language.