वाह ऊट्ः

The word वाह् is a ण्वि formed stem by 3.2.64. It can never stand alone, but, must be preceded by an upapada: hence we have used the word \compound.\ Thus प्रष्ठौहः, प्रष्ठौहा, प्रष्ठौहे, दित्यौहः, दित्यौहा, दित्यौहे ॥ By 6.1.108, ऊ + आ (of वा) = ऊ; and then प्रष्ठ + उह् = प्रष्ठौहः; the Vriddhi being substituted by 6.1.89. This form could have been evolved by simple samprasarana thus : प्रष्ठ + वह् + शस् = प्रष्ठ + उह् + अस् 6.1.108 = प्रष्ठ + ओह् + अस् (the affix ण्वि 3.2.64, will produce guna) = प्रष्ठौहः 6.1.88. In fact ण्वि is never added to वह् 3.2.64 unless the preceding member ends in अ and that अ + ओ of वा will always produce औ ॥ The making of this special samprasarana in ऊठ्, indicates the existence of following maxim: असिद्धं बहिरङ्गमन्तरङ्गे; and the samprasarana being a bahiranga operation, is considered as asiddha for the purposes of guna which is an antaranga operation : therefore, we can never get the form ओह ॥,