In the room of e or o (in the body of a word), + a of the case-affix as of the Ablative and Genitive Singular, the single substitute is the form of the precedent.,
Thus अग्ने + अस् = अग्नेः, वायोः ॥ The इ and उ of अग्नि and वायु are gunated by 7.3.111. This sutra applies when the ए or ओ are in the middle of a word and not padanta, as in the last. Thus अग्नेरागच्छति, वायोरागच्छति, अग्नेः स्वम्, वायोः स्वम् ॥,