A word ending with the Dative -4th case is compounded with what denotes that which is for the purpose of what ends with the Dative -4th case and so too with the words artha 'on account of', bali 'a sacrifice', hita 'salutary', sukha 'pleasure' and rakṣita 'kept' and the resulting compound is tat-puruṣa ,
The words सुप, सुपा are understood in this sutra and the whole sutra qualifies these words.
By the expression तदर्थ 'for the purpose thereof,' the special relation of a material and its modification alone is by Patanjali here held to be intended. As यूपाय दारुः = यूपदारुः 'wood for stake' (that is wood which by modification will be changed into a stake). कुण्डलहिरण्यं 'gold for ear-ring.' But not so here. रन्धनाय स्याली 'pot for cooking.' अवहननायोलूखलम् 'the wood mortar for threshing. From this sûtra we may also infer that the Dative case conveys also the sense of 'for the purpose thereof.' The word तदर्थार्थ is taken as one word by some, meaning 'a thing serviceable thereto.' See VI. 2. 44. For accent, see VI. 2. 45.
Vart:- With the word अर्थ the compound so formed is a Nitya compound (an invariable compound) and agrees in gender with the word which it qualifies; as, ब्राह्मणार्थम् पयः 'milk for the sake of Brahmans;' and ब्राह्मणार्था यवागूः 'gruel for the Brahmanas.' So also कुवेरबलिः 'a sacrifice for Kuvera_' महाराजबलिः 'a sacrifice for the great Raja.' गोहितं ' what is good for cows.' अश्वहितं 'what is good for horses' गोसुखं 'what is pleasant for cows' गोरक्षितं 'what is kept for cows,' (as grass).,