Bengali is an eastern Indo-Aryan language spoken mainly in Bangladesh (it is the official language of Bangladesh) and northern India. There are about 250 million native speakers of Bengali, and another 41 million people speak it as a second language.  As such, it is the 5th most spoken language by native speakers in the world, and the 7th most spoken overall.

The Bengali language movement from 1948 to 1956 demanded that Bengali be an official language of Pakistan.  This fostered Bengali nationalism in East Bengal, leading to the emergence of Bangladesh in 1971.  This is a wonderful instance of language leading to nation.

Bengali is a diglossia language, with a ‘high’ literary form and a ‘low’ spoken variety.  Sadhu bhasha (সাধু ভাষা "upright language") used to be the only written 'high' language, used in literary and religious settings.  Chôlito bhasha (চলিত ভাষা "running language"), known by linguists as Standard Colloquial Bengali, is a written Bengali style exhibiting a preponderance of colloquial idiom and shortened verb forms and is the standard for written Bengali now.

Within the spoken languages, dialects vary by religion.  Muslim speakers are more likely to use vocabulary borrowed from Persian and Arabic, while Hindu speakers are more likely to use words borrowed from Sanskrit.