Why is Ossetic not mutually intelligible with other Iranian languages?

The premise that Ossetic is not mutually intelligible with other Iranian languages is a consequence of its unique historical and geographical development. While Ossetic is an eastern Iranian language and a descendant of the ancient Alani and Sarmatian peoples, it has evolved in relative isolation from the main Iranian linguistic sphere.1

Ossetic occupies an exceptional position within the Iranian language family due to significant external influences that have fundamentally altered its character:

• Caucasian Influence: The phonology and vocabulary of Ossetic have been heavily shaped by prolonged contact with non-Indo-European Caucasian languages, particularly Georgian.12
• Loanwords: Unlike many other Iranian languages that share a common history of borrowing from Persian or Arabic, Ossetic’s borrowings from these sources often arrived indirectly through Turkish. In modern times, it has also been significantly influenced by Russian.2
• Archaic Preservation: While it preserves archaic features of Old Iranian, such as eight grammatical cases and verbal prefixes, these structures have diverged significantly from the development of other modern Iranian languages.1

These factors have created a distinct linguistic profile that limits mutual intelligibility with other members of the Iranian language family.2