Retroflex and dental consonants

Bangla has two full series of t- and d-like consonants, distinguished only by where the tongue touches. English has one, sitting roughly between them, which is why both series sound wrong at first and then sound identical.

For the retroflex series the tongue tip curls back to the roof of the mouth. For the dental series it presses forward against the back of the upper teeth — further forward than an English t ever goes.

The last row is the exception that proves how much of this is spelling: ণ and ন are written as a retroflex and a dental pair, but modern Bangla pronounces both exactly the same way.