The affixes meaning 'accomplished' etc. pantho ṇa nityam [[5.1.76]], tamadhīṣṭo bhṛto bhūto bhāvī [[5.1.80]] are necessarily elided after the word varṣā forming a dvigu samāsa (Numeral Determinative Compound) when it refers to being endowed with reason.,
Here the elision is compulsory and not optional as in the last. Thus द्विवर्षो दारकः 'a boy two years old'. Why do we say चित्तवति \when meaning endowed with reason\ ? Observe द्विवर्षीणो व्याधिः ॥,