Surjapuri is an Indo-Aryan language of the Bengali-Assamese branch, spoken in Eastern India including some eastern parts of Purnia division of Bihar, parts of Uttar Dinajpur district in West Bengal and Goalpara Division of Assam in India, as well as Jhapa district in Nepal and Thakurgaon district in Bangladesh.
It possesses similarities with Kamatapuri, Assamese, Bengali, and Maithili.
Surjapuri is associated with the Kamtapuri language (and its dialects Goalpariya, Rajbanshi and Koch Rajbangshi) spoken in North Bengal and Western Assam,[4] as well as with Assamese, Bengali, and Maithili.
Surjapuri has the oblique plural suffixes: sā (hamsā-, tomsā-) and smā (ismā-, usmā-).
They are also seen in Early Assamese as: sā (āmāsā-, tomāsā-) and sambā (esambā-, tesambā-) and their occurrences are similar.