hṛd is optionally substituted for hṛdaya before the words śoka and roga or the affix ṣyaṅ follow.,
Thus हृच्छोकः or हृदयशोकः, सौहार्द्यम् or सौहृदय्यम् ॥ Here ष्यङ् is added as हृदय belongs to Brahmanadi class (V. I. I24). When हृद् is substituted there is Vriddhi of both the members सु and हृ by 7.3.19. So also हृद्रोगः or हृदयरोगः ॥ All these forms could have been got from हृत् which is a full word sui generis, having the same meaning as हृदय ॥ The substitution taught in this sutra is rather unnecessary.,