अप् पूरणीप्रमाण्योः

The affix अप् comes after a बहुव्रीहि समास ending in a feminine ordinal numeral or in the word प्रमाणी।
The word पूरणी means words in the feminine gender ending in an ordinal affix 5.2.48 &c). प्रमाणा means 'a witness, a principal'. Thus कल्याणां पंचमी आसां रात्रीणां = कल्याणीपंचमा रात्रयः "the nights, the fifth of which is auspicious". कल्याणीदशमा रात्रयः ॥ So also स्त्री प्रमाणी एषां = स्त्रीप्रमाणाः कुटुम्बिनः meaning आर्याप्रधानाः "having a woman for authority".

Vart:- The affix अप् applies when the Ordinal Numeral is the principal (pradhana) member in a compound. When the Ordinal enters fully into another object, and is not merely wrapped up as it were in another object in a secondary way, there the Ordinal is the principal. The prohibition of punvad-bhava--the change of feminine into masculine ordained by 6.3.24 -- applies also to the Ordinal when it is pradhana. Therefore, the affix is not added here. कल्याणपंचमीकः पक्षः = कल्याणी पंचमी अस्मिन् पक्षे ॥

Vart:- The affix अप् comes after नेतृ when preceded by a word denoting asterism. As मृगनेत्रा रात्रयः = मृगो नेता आसां रात्रीणां "the night whose Ieader is the asterism mriga" so also पुष्यनेत्राः ॥ Why do we say "an asterism"? Observe देवदत्तनेर्तृकाः ॥

Vart:- The affix अप् comes after नेतृ in the Chhandas. As बृहस्पतिनेत्रा देवाः, सोमनेत्राः ॥

Vart:- The affix ठच् comes after the word मास when preceded by an ordinal having an affix denoting wages of service. Thus पंचको मासोऽस्य = पंचक मासिकः कर्मकरः मासिका कर्मकर so also दशकमासिकः कर्मकरः ॥ Sutra 5.1.56 gives the rule for forming words denoting 'wages' by adding कन् 5.1.22. Therefore दशकमासिकः means "an artist whose monthly wages are ten coins".