The forms upeyivān , nāśvān , nūcān are irregularly formed.,
These forms are thus evolved:- To the verb इ 'to go' with the preposition उप, the affix क्वसु is added: as उप + इ + क्वसु. The root is reduplicated: as उप + ई + इ + क्वसु. The reduplicate is here long ई by 7.4.69. This long ई does not coalesce with the short इ by the rules of sandhi; for then the rule by which this ई was introduced would have no scope. Now we add the augment इट् contrary and in opposition to the rule 7.2.67. and this is the irregularity. As उप + ई + इ + इट् + क्वसु. Then the root य is replaced by च by sutra 6.4.81. As उप + ई + य + इट् + क्वसु = उपेयिवस् 1st. sing. उपेयिवान्. The augment इट् is however dropped in those cases (भ) where वस्, is changed into उप्; because the insertion of इट् was itself an exceptional case of limited scope:- for while the general rules 7.2.75 &c. ordained it, the special rule of 7.2.67 prohibited it; and it was by prohibition of this prohibition that इट् was employed before वस्. Therefore in accusative plural we have उपेयुषः; instrumental sing उपेयुषा &c.
This irregular participle is not limited to the upasarga उप; we find such irregular forms with other upasargas and without them also; thus समीयिवान्, and ईयिवान् as well.
By the anuvritti of the word वा read in this aphorism, we have लुङ् &c. in the alternative. As in Aorist उपागात्, Imperfect उपैत्, Perfect उपेयाव ।
The word अनाश्वान् is thus formed:- To the verb अश् 'to enjoy' we add the negative particle अन; apply the affix क्वसु and do not insert the augment इट्; So, we have अन + अश् + क्वसु = अनाश्वस् 1st. sing. अनाश्वान्. In the alternative we have Aorist नाशीत्, Imperfect नाश्नात् and Perfect नाश.
The word अनूचानः is thus derived:- The affix कामच् is added in expressing the agent to the verb वच् preceded by अनु. In the alternative we have Aorist अन्ववोचत्, Imperfect अन्वब्रवीत्, Perfect अनूवाच.,