A word ending with the Instrumental -3rd case-affix when it denotes the agent or the Instrument, is compounded optionally with a word ending in a kṛtya affix, when exaggerated statement (whether of praise or of censure) is implied and the resulting compound is tat-puruṣa ,
As काकपेयानदी 'a shallow river' (so shallow that a crow may dip his beak into it and touch the bottom and drink). श्वलेह्य कूपः 'a shallow well' (so that a dog can lick water from the brink of it). वाष्पच्छेद्यानि तृणानि 'thin grass' (so fragile that it can be cut by vapour) कण्टकसञ्चेय ओदनः .
This sūtra is in a way a prolongation of the last .
Vart:-The phrase 'words ending in a kritya affix' must not be taken universally, only the kritya affixes यत् and ण्यत् are meant in the above sutras. The following are the kritya affixes :- तव्य, अनीय, यत्, क्यप्, ण्यत्, (see sutra III. 1.95-132). Therefore there is no compounding when the word ends in तव्य as in काकैः पातव्या.,