तुश् छन्दसि

The तुः is ablative of तृ which includes both तृन् and तृच् ॥ This extends the application of these affixes to words other than attributes. Thus अतिशयेन कर्ता = करिष्ठः (कर्तृ + इष्ठन् = कर् + इष्ठ by 6.4.154, तृ is elided) As आसुर्ति करिष्ठः, दोहीयसी धेनुः ॥ By Vartika under 6.3.35 दोहित्री is changed into masculine दोहितृ and then ईयस् is added, when तृ is elided by 6.4.154.,