Anusvara

Anusvara (Sanskrit: "")is the diacritic used to mark a type of nasal sound used in a number of Indic scripts. 
Depending on the location of the anusvara in the word and the language in which it is used, its exact pronunciation can vary greatly.
In the context of Sanskrit, anusvara may also refer also to the nasal sound itself.
অনুস্বার onushshar in Bengali is written as a circle above a slanted line (ং), and represents /ŋ/. It is used in the name of the Bengali language বাংলা [baŋla]. It has merged in pronunciation with the letter ঙ ungô in Bengali. Although the onushshar is a consonant in Bengali phonology, it is nevertheless treated in the written system as a diacritic in that it is always directly adjacent to the preceding consonant, even when consonants are spaced, apart in titles or banners: বাং-লা-দে-শ bang-la-de-sh, not বা-ং-লা-দে-শ ba-ng-la-de-sh for বাংলাদেশ Bangladesh It is never pronounced with the inherent vowel "ô", and it cannot take a vowel sign (instead, the consonant ঙ ungô is used pre-vocalically).
Devanagari script, anusvara is represented with a dot (bindu) above the letter (e.g. मं).