The affix yat comes in the sense of 'loved' after the word hṛdaya being in the Genitive -6th-Case in construction.,
The construction is shown by the aphorism itself. Thus हृदयस्य प्रियः = हृ꣡द्यः 'pleasant to the heart' e. g. हृद्यो देशः, हृद्यं वनम् ॥ But we cannot say हृद्यः पुत्रः, the word संज्ञायां 4.4.99 governs this sutra also, and thus restricts the meaning of the word.,