The augment āṭ is added to the case-endings of the Dative -4th Case, Ablative -5th case and Genitive 6th-Case singular after the stem called nadī -- yū stryākhyau nadī [[1.4.3]] etc.,
As कुमार्यै, किशोर्यै, ब्रह्मबन्ध्वै, धीरबन्ध्वै, कुमार्याः, किशोर्याः, ब्रह्मबन्ध्वाः, धीरबन्ध्वाः ॥,