The differences between Thanjavur and Palakkad sub-dialects are: The Iyengars, particularly those outside Tamil Nadu, speak a dialect retaining ancient lexicon from religious texts such as the Naalayira Divya Prabandham.
It retains minor adaptations of classical Tamil (Sentamil) words that are no longer in common usage.
This may be observed in the etymology of several words in the Brahmin Tamil lexicon such as namaskaram (greeting), tirtham (water), and bhakshanam (food offering).
Brahmin Tamil frequently preserves non-native phonology, which non-Brahmin Tamil assimilates to native pattern[3]The Ramanujan-Bright hypothesis which examined Brahmin Tamil in detail concluded - In general, the Brahmin dialect seems to show great innovation on the more conscious levels of linguistic change – those of borrowing and semantic extension—while the non-Brahmin dialect shows greater innovation in less conscious type of change—those involving phonemic and morphological replacements[3]Bright attributes these changes to the comparatively high literacy rate of the Brahmin community.
[5][7] However, since the 1950s and the gradual elimination of Sanskrit loan words from the spoken tongue, Brahmin Tamil has fallen into disuse and has been replaced by the Central and Madurai Tamil dialects, by non Brahmin communities, as the preferred spoken dialects for day-to-day use.
[4] The Vaishnavite Iyengars having a unique subdialect of Brahmin Tamil of their own, called the Sri Vaishnava Manipravalam which interested linguistics for its peculiar grammatical forms and vocabulary.
[16] The difference between the Smartha and Sri Vaishnava variants are currently limited to vocabulary, particularly to words related to ritual and familial ties, alone.