Before a taddhita affix having an indicatory ñ , ṇ or k , the words yathātatha and yathāpura may have vṛddhi of the first vowel of their first member or that of the second member, in alteration.,
That is, when the Negative particle gets the vriddhi, the words remain unchanged; and when these words are vriddhied, the negative particle remains unaltered. As आयथातथ्यम् or अयाथातथ्यम्, आयथापुर्यम् or अयाथापुर्यम् ॥ The words अयथातथ and अयथापुर should be considered to belong, as negative compounds, to Brahmanadi class 5.1.124: and take ष्यञ् ॥ In the sutra the compounds यथातथ and यथापुर are exhibited and are Avyayibhavas 2.1.7, and being neuters, the आ of तथा and पुरा are shortened. According to Patanjali this sutra is superfluous. When the negative particle takes Vriddhi, the compound should be analysed as, न यथातथा = अयथातथा, अयथातथा भावः = आयथातथ्यम् ॥ When the second member gets the vriddhi, the compound should be analysed as, यथातथा भावः = याथातथ्यं, न याथातथ्यम् = अयाथातथ्यम् ॥,