कर्मव्यतिहारे णच् स्त्रियाम्

The affix णच् comes after a root in denoting reciprocity of action and the word so formed is in the feminine gender.
The word कर्म means 'action' and is not the technical 'Karma' meaning the accusative case. व्यतिहार means reciprocity or interchange of action. The word so evolved is feminine in form and denotes mere 'action' (भाव) also. The anubandha च in णच् is qualitative and is added to distinguish this affix from other affixes: thus in sutra 5.4.14 this particular affix is meant.

Thus वि + अव + क्रुश् + णच् + अञ् + ङीष् = व्यावक्रोशी 5.4.14 and 7.3.6 'mutual abuse'. So also व्यावहासी, व्यावलेखी. The affix णच् forms only an imaginary stem; for this stem must take the affix अञ् by 5.4.14, which even does not form the complete word until the affix ङीष् of the feminine is added.

Why do we say 'in the feminine'? Observe व्यतिपाको वर्तते ।

The making of this a separate sutra by itself and not reading it in the subdivision of feminine affixes beginning with क्तिन् 3.3.94 is for the sake of removing the obstructing aphorisms that would otherwise have prevented the application of this rule.

For, had it been taught in connection with क्तिन् &c, then the affixes that would have debarred क्तिन् &c, would a fortiori have debarred this also. But by keeping it separate from that class, it is indicated that those obstructive affixes which debar क्तिन् &c, do not debar this. Thus व्यावचोरी, व्यावचर्ची । Here चुर् being a ण्यन्त class root would have taken युच् 3.3.107 in the feminine, as चोरणा; and चर्च् would have taken अङ् by 3.3.104, as चर्चा. The roots ईक्ष् and ईह्, by 3.3.102 & 3.3.103, take अ by debarring क्तिन् । This debarring affix अ, however, is not debarred by this rule; as व्यतीक्षा, व्यतीहा are the proper feminine forms, and not व्यतीक्षी &c. The form व्यातुक्षी is, however, an apparent exception. All these exceptions, counter-exceptions &c. are examples of बहुलं taught in 3.3.113.