Surjapuri is an Indo-Aryan language of the Bengali-Assamese branch, spoken in Eastern India including some eastern parts of Purnia division (Kishanganj, Katihar, Purnia, and Araria districts) of Bihar, parts of Uttar Dinajpur district in West Bengal and Goalpara Division of Assam in India, as well as parts of Thakurgaon district in Bangladesh and Jhapa district in Nepal. Among speakers in some regions, it is known as 'Deshi Bhasa'. It possesses similarities with Kamatapuri, Assamese, Bengali, and Maithili.
Surjapuri is mainly spoken in some parts of Purnia division (Kishanganj, Katihar, Purnia, and Araria districts) of Bihar. It is also spoken in West Bengal (some parts of Islampur subdivision of Uttar Dinajpur district and Jalpaiguri division in northern Bengal region), Bangladesh (Thakurgaon District) as well as in parts of eastern Nepal of Jhapa District and Morang District.
Surjapuri is associated with the Kamtapuri language (and its dialects Goalpariya, Rajbanshi and Koch Rajbangshi) spoken in North Bengal and Western Assam, as well as with Assamese, Bengali, and Maithili.
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Surjapuri has the oblique plural suffixes: sÃÂ (hamsÃÂ-, tomsÃÂ-) and smÃÂ (ismÃÂ-, usmÃÂ-). They are also seen in Early Assamese as: sÃÂ (ÃÂmÃÂsÃÂ-, tomÃÂsÃÂ-) and sambÃÂ (esambÃÂ-, tesambÃÂ-) and their occurrences are similar.