A B G D Terms

A B G D Terms
A b g d as the first 4 letters of alphabets relate to abugidas.  
In terms of Sanskrit A B G D represents: Vowel 1 - Letter 23 - Letter 3 - Letter 13
This seemingly random sequence becomes meaningful when we view it in terms of the 25 letter consonant matrix of Sanskrit where they occupy the middle line: 
                                     G = 3
                                     D = 13
                                     B = 23 
* Sanskrit Consonants
non manifest sounds manifest sounds
B as Sanskrit letter 23 is the beginning of audible sounds.
If we imagine the square in an alphabet circle, with B as the Summer Solstice, then we can imagine a spiral of involution from b to g and ending in d (death, letter 13). It is noteworthy that the letter b in Indicum (q.v.) and other languages is drawn as a spiral.