वचिस्वपियजादीनां किति

The semi-vowels of the roots वच् , स्वप् , and यजादि verbs are vocalised when followed by an affix having an indicatory क।
The anuvritti of ष्यङ् does not run into this sutra. The root वच includes the वच परिभाषने of the Adadi class (II.54) and the वच् substitute of ब्रू 2.4.53 स्वप् is the root ञिष्वप् शये of the Adadi class (II 59). The यजादि verbs are the last nine roots of the Bhvadi class viz. यज्, वप्, वह, वस्, वेञ्, ष्येञ्, ह्वेञ्, वद् and श्वि ॥ The semivowels of these eleven verbs are changed into the corresponding vowel, when an affix having an indicatory क is added to them. Thus with the Past Participle affixes क्त and क्तवतु third we have the following forms:- वच् -उक्तः, उक्तवान् , 8.2.30. 2 स्वप् - सुप्तः, सुप्तवान् 3 यज् - इष्टः, इष्टवान्. 8.2.36 4 वप् -उप्तः, उप्तवान्, 5 वह् - ऊढः, ऊढवान् 8.2.31, 8.2.40, 8.3.13 and 6.3.111 6 वस् - ऊषितः ऊषितवान्, 7.2.56 8.3.60 7 वेञ् - उतः, उतवान्, 8 व्येञ् - संवीतः, संवीतवान्, 9 ह्वेञ् - हूतः, हूतवान्, 10 वद् - उदितः, उदितवान् , 11 दुओश्वि - शूनः, शूनवान् ॥

धातो स्वरुपग्रहणे तत्प्रत्यय कार्ये विज्ञायतेः- When in a Grammatical rule, an operation (dependant on an affix) is taught with regard to a root (dhatu) by mentioning particular verbs (dhatu) specifically, and not by using the word "dhatu", generally, then the operation takes place only when the root is followed by such an affix as can be added to roots by emunciating the word धातोः ॥ The existence of this maxim is inferred in the formation of the word भ्रौणहत्यम् in 6.4.174, which see. Therefore, there is no vocalisation of वच् in the following वाच्यति, वाचिकः ॥ Here वाच्यति is formed by adding क्यच् to वाच् (वाचमिच्छति)॥ वाच् is formed by क्विप् added to वच्, the vowel being lengthened and samprasarana being expressly prevented by Unadi II.57. Now, it is a general rule that a root taking the affix क्विप्, विट्, or विच् does not lose its character of a dhatu. Therefore वाच् is a root (धातु), and it ought to take vocalisation before the affix क्यच् ॥ But क्यच् is not enunciated to come after a dhatu, but after a सुबन्त (सुपआत्मनः क्यच् 3.1.8) in the rule ordaining its affixing. So also वाचिकः formed by adding ठक् to वाच् (See Vartika V. 3.83).