आन्महतः समानाधिकरनजातीययोः

As महादेवः, महाब्राह्मणः, महाबाहुः, महाबलः, महाजातीयः ॥ But महतः पुत्रः = महत्पुत्रः \the son of the great man\: the two words are not in apposition. The compounding with महत् takes place under 2.1.61. This rule applies to compounds under that rule, as well as to Bahuvrihis, when also the two words are in apposition, as in महाबाहुः ॥ In fact this is the object of using the word samanadhikarana in this sutra. Had it not been used, then by the maxim of pratipadokta, the rule would have applied only to the Tatpurusha compounds of mahat taught under (II. I. 61) but not to Bahuvrihis. In महद्भूतश्चन्द्रमा = अमहान् महान् संपन्नः, the long आ is not substituted, as the sense of महत् is here secondary.

Vart:- आ is substituted for the final of महत् before घास, कर and विशिष्ट, the feminine महती being changed to masculine, though the words may not be in apposition. As महत्या घासः = महाघासः, महत्याः करः = महाकरः, महत्याविशिष्टः = महाविशिष्टः ॥

Vart:- आ is substituted for the final of अष्टन् before कपाल, when a sacrificial offering is meant. As अष्टाकपालं चरुं निर्वपेत ॥ Why do we say when meaning a sacrificial offering? Observe अष्टकपालं ब्राह्मणस्य ॥

Vart:- आ is substituted for the final of अष्टन् before गौ, when the meaning is that of 'yoked'. As, अष्टागवेन शकटेन ॥ But अष्टगवं ब्राह्मणस्य, where 'yoking' is not meant. The त् in आत् is for the sake of distinctness.,