In all the remaining feminine words called nadī -- yū stryākhyau nadī [[1.4.3]] and neyaṅuvaṅsthānāvastrī [[1.4.4]], the substitution of short vowel under the preceding circumstances is optional.,
What are the शेष or the remnants? Those feminines which are not formed by long ई (ङी), and are called Nadi; and those feminines which end in long ई but consist of one syllable. Thus ब्रह्मबन्धूतरा or ब्रह्मबन्धुतरा वीरबन्धूतरा or वीरबन्धुतरा, स्त्रितरा or स्त्रीतरा, स्त्रितमा or स्त्रीतमा ॥
Vart:- Nadi words formed by कृत् affixes are excepted: as लक्ष्मीतरा, तन्त्रीतरा formed by the Unadi affix ई (Unadi III. I58, 160),