Definition: a collection of letters or alphabet given traditionally. Although the Sanskrit alphabet has got everywhere the same cardinal letters i.e. vowels अ, इ etc., consonants क्, ख् etc : semivowels य्, र्, ल्, व, sibilants श् ष् स् ह् and a few additional phonetic units such as अनुस्वार, विसर्ग and others, still their number and order differ in the different traditional enumerations. Panini has not mentioned them actually but the fourteen Siva Sutras, on which he has based his work, mention only 9 vowels and 34 consonants, the long vowels being looked upon as varieties of the short ones. The Siksa of Panini mentions 63 or 64 letters, adding the letter ळ (दुःस्पृष्ट); cf. त्रिषष्टि: चतुःषष्टिर्वा वर्णाः शम्भुमते मताः Panini Siksa. St.3. The Rk Pratisakhya adds four (Visarga, Jihvamuliya, Upadhmaniya and Anusvara) to the forty three given in the Siva Sutras and mentions 47. The Taittiriya Pratisakhya mentions 52 letters viz. 16 vowels, 25class consonants, 4 semivowels,six sibilants (श्, ष्, स्, ह्, क्, प्,) and anusvara. The Vajasaneyi Pratisakhya mentions 65 letters 3 varieties of अ, इ, उ, ऋ and लृ, two varieties of ए, ऐ, ओ, औ, 25 class-consonants, four semivowels, four sibilants, and जिह्वामूलीय, उपध्मानीय, अनुस्वार, विसर्जनीय, नासिक्य and four यम letters; cf. एते पञ्चषष्टिवर्णा ब्रह्मराशिरात्मवाचः V. Pr. VIII. 25. The Rk Tantra gives 57 letters viz. 14 vowels, 25 class consonants, 4 semivowels, 4 sibilants, Visarga,.Jihvamuliya, Upadhmaniya, Anunasika, 4_yamas and two Anusvaras. The Rk Tantra gives two different serial orders, the Uddesa (common) and the Upadesa (traditional). The common order or Uddesa gives the 14 vowels beginning with अ, then the 25 class consonants, then the four semivowels, the four sibilants and lastly the eight ayogavahas, viz. the visarjanya and others. The traditional order gives the diphthongs first, then long vowels (अा, ऋ, लॄ, ई and ऊ) then short vowels (ऋ, लृ, इ, उ, and lastly अ), then semivowels, then the five fifth consonants, the five fourths, the five thirds, the five seconds, the five firsts, then the four sibilants and then the eight ayogavaha letters and two Ausvaras instead of one anuswara. Panini appears to have followed the traditional order with a few changes that are necessary for the technigue of his work.