After a aṅga (stem) ending in short i and u and which is not nadī -- yū stryākhyau nadī [[1.4.3]] or ghi -- śeṣo ghyasakhi [[1.4.7]], au is substituted for the i of the Locative -7th case singular.,
As सख्यौ, पत्यौ ॥
In the case of नदी words आम् is taught by the previous sutras; in the case of घी words औ preceded by अ substitution of घि letters will be taught in the next sutra, so by the rule of exclusion, the present sutra applies to words other than nadi and ghi.,