The a of the Aorist characteristic kas is elided before an affix beginning with a vowel.,
As अधुक्षाताम्, अधुक्षाथाम्, अधुक्षि from the root दुह् ॥ Had the अ not been elided before आताम् and आथाम्, then इय must have been substituted for it according to 7.2.81. Why do we say before an affix beginning with a vowel? Observe अधुक्षत्, अधुक्षताम् ॥ Why do we say क्स and not only स? So that the elision should not take place here, as उत्सौ, उत्साः, वत्सौ, वत्साः, तृणसौ, तृणसः ॥,