This (concord or gender and number, of primitive and derivative nouns, and of attributes and substantives need not be taught (or approved), because it has the authority of saṃjñā (conventional term or idiom).,
The agreement between the number and gender of the nouns and attributes; of primary and secondary words formed by suffix rejection, is not an approved syntax. The gender and number of particular derivatives or adjectives are not blindly to be fixed by the primary words or the governed substantives; but it is a matter more or less of usage or idiom: and no hard and fast rule can be laid down for it. Thus the word दाराः 'wife' has the form of masculine plural, but is always applied to females, similarly आपः 'water' is always feminine plural in form, so also गृहाः वर्षाः सिकताः. This sutra, therefore, modifies the former sutras and leaves the whole question of syntactic agreement to be decided by usage and idiom.
The words like Panchalas, Kaurava, &c, should not be considered as derivative words formed by the lup elision of Taddhita; but they must be taken as proper nouns and appellatives of certain countries; consequently the gender and number of such words are fixed by the nature of such words and not by any rule of grammar.,