Rarhi dialect

Rarhi (;) or Central Standard Bengali is a dialect of Bengali language spoken in the southeastern part of West Bengal, in and around the Bhagirathi River basin of Nadia district and the Presidency division in West Bengal, as well as the Greater Kushtia region of western Bangladesh. It forms the basis of the standard variety of Bengali.
Geographical boundaries.
This dialect is prevalent in the West Bengali districts of Kolkata, North 24 Parganas, South 24 Parganas, Nadia, Howrah, Hooghly and Purba Bardhaman. It is also spoken natively in the Chuadanga, Kushtia and Meherpur districts of Bangladesh, which were a part of the Nadia district prior to the 1947 Partition of India. Modern Standard Bengali has been formed on the basis of this dialect.
Features.
Extensive use of "Obhishruti" (অভিশ্রুতি, /obʱisrut̪i/). E.g. old Bengali Koriya (করিয়া, /koria/, meaning - having done) > Beng. Koira (কইরা, /koira/) > Beng. Kore (করে, /kore/).
Obhishruti and Opinihiti.
"Ôbhishruti" (অভিশ্রুতি, /obʱisrut̪i/) and "Ôpinihiti" (অপিনিহিতি, /opinihit̪i/) are two phonological phenomena that occur in spoken Bengali. Opinihiti refers to the phonological process in which a "ই" or "উ" is pronounced before it occurs in the word. Obhishruti is the sound change in which this shifted "ই" or "উ" becomes removed and changes the preceding vowel. Observe the example above : Koriya (করিয়া, /koria/) > Koira (কইরা, /koira/) > Kore (করে, /kore/). First Opinihiti changes Koriya to Koira (notice how the I changes position.), then Obhishruti changes Koira (কইরা) to Kore (করে).