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 three sub groups: Jaffna Tamil, Batticaloa Tamil 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.