Sylheti is an Indo-Aryan language that is a member of an Indo-European language group. Other branches of the Indo-European language group include Celtic, Germanic, Balto-Slavic and Indo-Aryan to name but a few.
Sylheti originally developed from Hindustani (Hindi/Urdu) spoken in India and Bangladesh. It is often considered as a dialect of Bengali and, although it is not mutually intelligible with Standard Bengali, 80% of Sylheti vocabulary is shared with Bengali.
Sylheti used to be written with its own script; however, this script is now nearly extinct. Sylheti is now normally written with the Bengali script due to a policy of the Government of Bangladesh to promote a unified Bengali identity.