The affix lyuṭ is added to a root when the name of an action is expressed, in the neuter gender provided that the verb has in construction with it, such a word in the Accusative -2nd case, as indicates the thing, from the contact with which, there arises a pleasant sensation corporally to the agent.,
This sutra is thus translated by Bohtlingk:-\The affix ल्युट् comes in connection with an object, when through the contact with that, the agent of the action feels a lively pleasure\. Though the affix lyut would have presented itself by the last aphorism, under the circumstances mentioned in this sutra, the framing of this sutra, is really for the purpose of teaching, that the compound so formed is a नित्य or invariable compound i. e. a compound which cannot be analysed into its component members:--for every उपपद compound is a नित्य compound. 2.2.19 Thus पयः पानंसुखं 'the pleasure of drinking milk'; ओदनभोजनं सुखं 'the pleasure of eating rice'.
Why do we say 'when the word in construction is in the accusative case'? Observe तूलिकाया उत्थानं सुखं 'rising from a bed of down is pleasant'. Here there is no compounding as the upapada तूलिका is in the ablative case.
Why do we say 'from the contact'? Observe अग्निकुण्डस्योपासनं सुखं 'it is pleasure to sit near by a fire-hearth'. Here there being no contact between 'fire' and 'body', there is no compounding.
Why do we say 'to the agent'? Observe गुरोः स्नापनं सुखं 'to the teacher it is pleasure, when he is made to bathe'. Here the word गुरुः is not the agent, but the object of the verb स्नापयति ।
Why do we say 'corporally'? Observe पुत्रस्य परिष्वञ्जनं सुखम् 'embracing of the son is a pleasure'. Here the pleasure is a mere mental satisfaction and not a physical one.
Why do we say 'a pleasant sensation'? Observe कण्टकानां मर्दनं दुःखम् 'it is painful to rub thorns'. In all the above counter-examples there is no compounding; see 2.2.19 and the connected sutras.,