आदेशप्रत्यययोः

The word cerebral is understood here from 8.3.55, as well as स ॥ The sutra adesa-pratyayoh is in the Genitive case. The force of the Genitive however is different in the word adesa, from what it is in pratyaya. In the first it is samanadhikarana-shashthi, in the latter avayava-yogashashthi. That is that स् which is an adesa, and that स् which belongs to an affix. If we took it as avayavayoga shashthi in both places, then the sutra would mean \of that स् which is a portion of a substitute, or of an affix,\ and there would arise the following anomaly. In doubling a word by 8.1.1, one view is that two are substituted in the room of one (See 8.1.1). Thus बिसंबिसं, मुसलंमुसलं ॥ Here the स् in these words, is a portion of a substitute, and would be changed to ष्, if we translate the sutra as above.

If we take the other view, and translate the sutra as \of that स् which is a substitute or an affix\, we land on the following anomaly. We must have forms like करिस्यति and हरिस्यति, and not the correct forms करिष्यति, हरिष्यति; for here स is not an affix, but a portion of an affix. In fact, with regard to affixes, the sutra would be confined to those affixes only which consist of a single स्, such as सिप् in the Vedic subjunctive लेट् ॥ That this is the proper interpretation of the sutra is indicated by the sutra 8.3.60, (the next aphorism). The substitute घस् is taken in this sutra. If therefore, the force of Genitive in आदेशस्य was = आदेशस्य यः सकारः and not = आदेशः यः सकारः, then there would have been no necessity of including the substitute घस् in the sutra, for then the present sutra would have covered the case of घस् also. Similarly, if the force of the Genitive in प्रत्ययस्य was = प्रत्ययः यः सकारः, and not = प्रत्ययस्यः यः सकारः; then there would have been no necessity of excluding the affix सात् 5.4.52 from the operation of the present rule by 8.3.111, because it is not an affix consisting of a single letter स् ॥

Having surmised this, we shall now give illustrations. First of that स् which is a substitute. It can only be the स् which replaces the ष् of a root in Dhatupatha. Thus सिषेव, सुष्वाप ॥ Of an affix, we have अग्निषु, वायुषु, कर्तृषु, हर्तृषु; वक्षत् in इन्द्रो मा वक्षत्; and यक्षत् in स देवान् यक्षत् ॥

In the case of वक्षत् and यक्षत्, the स् is not the portion of an affix, but the whole affix itself: the present sutra should therefore not apply to this स् ॥

Answer:- Here we apply the maxim व्यपदेशिवद् एकस्मिन् ॥

These words (वक्षत् and यक्षत्) are from the roots वच् and यज्, in लेट् with तिप्, the इ is elided by 3.4.97, the augment अट् 3.4.94, the affix सिप् by 3.1.34; the च् of वच् is changed to a guttural, and the ज् of यज् to ष् and then to a guttural.

The Unadi word अक्षरं (अश् + सर् Unadi III. 70) complies with this rule, but not so the word कूसरं and धूसरं (Unadi_ III. 73) formed with the same affix सर ॥,