पूर्वरूप-सन्धि

When ए or ओ at the end of a word is followed by अ in a sentence, then अ merges with the initial ए or ओ and " ऽ "(अवग्रह) is substituted for अ.

• विष्णो + अव = विष्णोऽव ।
• हरे + अव = हरेऽव ।
• रामः + अवति = रामो + अवति = रामोऽवति ।
  (The change of अः to ओ will be explained later)   

Note : The horizontal stroke is not put over the " ऽ "(अवग्रह). This सन्धि can be said to be an exception of अयादि-सन्धि.