Sri Lankan Tamil dialects
The Sri Lankan Tamil dialects or Ceylon Tamil dialects form a group of Tamil dialects used in the modern country of Sri Lanka by Sri Lankan Tamil people that is distinct from the dialects of modern Tamil spoken in Tamil Nadu and Kerala states of India. Tamil dialects are differentiated by the phonological changes and sound shifts in their evolution from classical or Old Tamil (300 BC - 700 CE). It is broadly categorized into four sub groups: Jaffna Tamil, Batticaloa Tamil, up country Indian origin Tamils and Negombo Tamil dialects. These dialects are also used by ethnic groups other than Tamils such as Sinhalese people, Sri Lankan Moors and Veddas, who consider them to be distinct. These dialects are not mutually intelligible with Indian Tamil dialects, which some of the native speakers consider to be a separate language.
As Tamil is a diglossic language the differences between the standard written languages across the globe is minimal but the spoken varieties differ considerably. The spoken varieties in Sri Lanka although different from those of Tamil Nadu share some common features between the southern dialects of Tamil Nadu and the northern Sri Lankan Tamil dialect, the language of Jaffna. Sri Lankan Tamil dialects retain many words and grammatical forms that are not in everyday use in India, and use many other words slightly differently. The Sri Lankan Tamil dialects are less influenced by Sanskrit and the western languages, although there are western and Sanskrit loan words in day to day usage. In general Sri Lankan Tamil dialects are considered to be more conservative than the continental Tamil dialects.
The Negombo Tamil dialect used in Negombo area by bilingual fishers who otherwise identify them as Sinhalese has undergone considerable morphosyntactic convergence with spoken or colloquial Sinhala, as a consequence of contact with it. It has also developed a number of other grammatical traits under the probable influence of Sinhala, including a postposed indefinite article, an indefinitizing postclitic –sari (apparently modeled on Sinhala –hari), and case assignments for defective verbs that follow the Sinhala, rather than Tamil, patterns of agreement.
Batticaloa Tamil dialect is shared between Tamils, Moors, Veddhas and Portuguese Burghers in the eastern province. The Tamil dialect used by residents of the Trincomalee district has many similarities with the Jaffna Tamil dialect. According to Kamil Zvelebil a linguist, the Batticaloa Tamil dialect is the most literary like of all spoken dialects of Tamil, and it has preserved several very antique features, and has remained more true to the literary norm than any other form of Tamil while developing a few striking innovations. Although Batticaloa Tamil has some very specific features of vocabulary, it is classified with other Sri Lankan Tamil dialects as it is related to them by characteristic traits of its phonology. It also maintains some words that are unique to present day .
The dialect used in Jaffna is the oldest and most archaic and is claimed to be closest to Tamil Nadu Tamil. It is considered to preserve many antique features of Old Tamil that predate Tolkāppiyam, the grammatical treatise of Tamil. The Jaffna Tamil dialect retained many forms of words which were used in Sangam literature such as Tirukkuṛaḷ and Kuṟuntokai. Jaffna Tamil dialect is mutually intelligible with Indian Tamil dialects, though both share a diglossic `H' variety in literary Tamil. It is frequently mistaken for Malayalam by native Indian Tamil speakers. There are a number of Prakrit loans words that are unique to the Jaffna Tamil. A subdialect retained by the Paraiyar people of Kayts still retains a number of archaic words and Prakrit loans found in any other dialects of Tamil. These drummers had historically played an important role as ritual players of drums at funerals and folk temples and as heralds and traditional weavers. They also maintained the family records of their feudal lords and even practiced medicine and astrology in folk traditions 
- Thomas Lehmann, "Old Tamil" in Sanford Steever (ed.), The Dravidian Languages Routledge, 1998 at p. 75; E. Annamalai and S. Steever, "Modern Tamil" in ibid. at pp. 100-128.
- Kamil Zvelebil, "Some features of Ceylon Tamil" Indo-Iranian Journal 9:2 (June 1966) pp. 113-138.
- Indrapala, K The Evolution of an ethnic identity: The Tamils of Sri Lanka, p.46
- Contact-Induced Morphosyntactic Realignment in Negombo Fishermen’s Tamil By Bonta Stevens, South Asian Language Analysis Roundtable XXIII (October 12, 2003) The University of Texas at Austin
- Negombo fishermen's Tamil: A case of contact-induced language change from Sri Lanka by Bonta Stevens, Cornell University
- Kuiper, L.B.J (March 1964). "Note on Old Tamil and Jaffna Tamil". Indo-Iranian Journal. Springer Netherlands. 6 (1): 52–64. doi:10.1007/BF00157142.
- Subramaniam, Folk traditionas and Songs..., p.9-10
- Shanmugathas, A. "Yalpana Thamilil Sangath Thamil" (in Tamil). Retrieved 1 April 2010.
- Schiffman, Harold (1996-10-30). "Language Shift in the Tamil Communities of Malaysia and Singapore: the Paradox of Egalitarian Language Policy". University of Pennsylvania. Retrieved 2008-04-04.
- Indrapala, K The Evolution of an ethnic identity: The Tamils of Sri Lanka, p.45
- Indrapala, K The Evolution of an ethnic identity: The Tamils of Sri Lanka, p.389
- Ragupathy, Tamil Social Formation in Sri Lanka: A Historical Outline, p.1
- Indrapala, Karthigesu (2007). The evolution of an ethnic identity: The Tamils in Sri Lanka C. 300 BCE to C. 1200 CE. Colombo: Vijitha Yapa. ISBN 978-955-1266-72-1.
- Subramaniam, Suganthy (2006). Folk Traditions and Songs of Batticaloa District. Kumaran Publishing. p. 99. ISBN 0-9549440-5-4.