न वृद्भ्यश्चतुर्भ्यः

The परस्मैपद आर्धधातुक affixes beginning with स् do not get the इट् augment after वृत् and the three roots (वृध् , शृध् and स्यन्द्) that follow it.
Thus वृत् — वर्त्स्यति, अवर्त्स्यत्, विवृत्सति । वृध् वर्त्स्यति, अवर्त्स्यत् । विवृत्स्सति । शृधू । शर्त्स्यति । अशर्त्स्यत् । शिशृत्सति । स्यन्दू । स्यन्त्सति । अस्यन्त्स्यत् ।

The वृतादि roots are four वृत्, वृध्, शृध् and स्यन्द (Bhuadi 795-798). In the examples, the Parasmaipada forms are shown, because these roots are optionally Parasmaipadi by 1.3.92 before स्य and सन् ॥

Objection :- The word चतुर्भ्यः may conveniently have been omitted from the sutra. A reference to the Dhatupatha will show that the वृतादि roots form a subdivision of द्युतादि roots, and stand at the end of Dyutadi class. So that the sutra न वृद्भ्यः would have been enough, and there would have been no uncertainty or vagueness about it, for the word वृतादि would mean 'the roots वृत् &c. with which the Dyutadi class ends'. Thus we shall get the five roots 795 वृतुर्वर्तने 796 वृधु वृद्धौ, 797 शृधु शब्दकुत्सायाम्; 798 स्यन्दू प्रस्रवणे and कृपू सामर्थ्ये ॥ As regards the last root कृपू, we shall find from the next sutra, that the present sutra applies to this root also. Or we can change the order of the roots, putting कृपू first, and वृतु &c after it, so that वृतादि will mean four roots only. Whether vritadi be taken to mean the five or the four roots, the word चतुर्भ्यः is redundant.

Ans:- The word चतुर्भ्यः is used in order that the prohibition contained in this sutra may debar the 'option' which the root स्यन्दू would have taken, because of its indicatory long ऊ 7.2.44. For this 'option' is an antaranga operation, because it applies to all ardhadhatuka affixes; while the 'prohibition' of the present sutra is a bahiranga, because it applies to those affixes only which begin with स ॥ So that the 'prohibition' of this sutra would not have debarred the 'option' of 7.2.44: and in the Parasmaipada स्यन्दू would have had two forms; which, however, is not the case because of the word चतुर्भ्यः by which the 'prohibition' is extended to स्यन्दू also. Thus in the Parasmaipada, we have only one form, as, स्यन्त्स्यति; but in the Atmanepada we have two forms स्यन्दिष्यते or स्यन्त्स्यते ॥

The word 'Parasmaipada' is understood in this sutra, so that the prohibition does not apply to atmanepada affixes: as वर्त्तिषीष्ट, वर्तिष्यते, अवर्तिष्यत्, विवर्तिष्यते, स्यन्दिषीष्ट or स्यन्त्सीष्ट ॥ Moreover, with regard to Atmanepada also, the इट् is added to these roots when they stand in the same 'pada' with the affixes. But when the Atmanepada affixes are added not to the roots 'vrit &c', but to the roots which are derived from the nominal bases formed from 'vrit &c', then the 'root' is not in the same pada with the affix, and the prohibition of this sutra will apply. As विवृत्सित्रीयते ॥ Moreover, the rule applies, as we have said, to the affixes standing in the same 'pada' with the 'roots'; therefore it will apply to Desiderative roots, as विवृत्सति, though शप् here intervenes between the ardhadhatuka affix सन् and the Parasmaipada तिप्; so also, an ekadesa though sthanivat and therefore an intervention, will not be considered so for the purposes of this rule, as विवृत्सिष्यति; so also in विवृत्सयति ॥ This prohibition, moreover, applies to कृत् affixes, and where there is luk-elision of Parasmaipada affixes. As विवृत्सिता; and विवृत्स त्वम् where the Imperative हि is luk elided, and being so elided, the force of Parasmaipada does not here remain by न लुमताङ्गस्य 1.1.63; hence the above Ishti.