There are 14 অ বর্গীয় (O borgiyo) letters in Bengali. But couldn't find out in book what they are. I know that there are 11 vowel letters in Bengali. But while looking for অ বর্গীয়, I just found that there are 14 vowel letters^{English Wikipedia Bangla Wikipedia}. I suspect they are referring to অ বর্গীয়. Since their numbers are equal and every single book in Bangla says that there are 11 vowel letters.

In Wikipedia, I found a new letter ৡ. It is called দীর্ঘ ঌ according to Bangla Wikipedia (Unicode can't be detected in English Wikipedia properly). What does it mean? Even I haven't seen anyone using the letter. There was another similar letter which is ঌ. Generally, It is equivalent to "9" in English. But, the Bangla Wikipedia call it হ্রস্ব ঌ. Even I have never seen these kind of conjunctive earlier.

How do these letters work in Bangla?