Siddham Pa 𑖢

Pa heads the labial class, the last of the five, made by closing the lips, which is the outermost point of articulation and therefore the last position in an order that runs from the throat forwards. With this class the twenty-five stops are completed.

The Sanskrit phoneticians call the class oshthya, of the lips, and they group the vowels u and long u with it, since those are formed with the lips as well. That cross-reference between the vowel table and the consonant table is one of the clearest signs that the arrangement is a genuine analysis of speech rather than a convenient ordering: the same articulatory categories are applied to both halves of the inventory, and the categories are the point.

The letter is common in the vocabulary, standing in a large number of roots including several that generate substantial families of derived terms, and it appears in a set of very frequent prefixes. It takes the full range of vowel marks and enters conjuncts freely, most often with the semivowel ra and with the sibilants.

Its position at the head of the class is fixed by the same rule as every other class head: voiceless, unaspirated, the plainest treatment of the sound made at that point.

The five classes of stops are ordered by where in the mouth the closure is made, and the sequence runs from the furthest back to the furthest forward: the soft palate, the hard palate, the roof of the mouth with the tongue curled back, the teeth, and the lips. Reciting the twenty-five letters in order is therefore a movement through the mouth in one direction, and a learner rehearsing the sequence is rehearsing the anatomy.

The scheme carries several claims that were not obvious and turned out to be right. That speech sounds can be classified by place of closure. That the same set of features, voicing and aspiration and nasality, applies at every place. That vowels and consonants can be described in the same terms, which is why the vowels are grouped with the classes they share an articulation with. Modern phonetics arrived at all of these independently, much later, and describes them with a similar grid.

What the Indian tradition did not have was a way of writing the analysis except as a list of letters, so the table is both the description and the alphabet. That fusion is the reason the order travelled: a script can be adopted for practical reasons and carry a theory with it, which is more or less what happened when the Siddham letters reached China and Japan.