For the i of the root iṇ (eti) is substituted a semi-vowel (ya) before the affix beginning with a vowel.,
Thus यन्ति, यन्तु, आयन् ॥ This supersedes इयङ् substitution, and is itself superseded by 7.2.115, and 7.3.84 which ordain Vriddhi and Guna: on the maxim मध्येऽपवादाः पूर्वान् विधीन् बाधन्ते, नोत्तरात् ॥ \Apavadas that are surrounded by the rules which teach operations that have to be superseded by the apavada operations, supersede only those rules that precede, not those that follow them.\ So we have अयनम् and आयकः ॥,