The disappearance of an affix when it is caused by the words luk , ślu or lup are designated by those terms respectively.,
When an affix is elided by using the term luk, that disappearance gets the appellation of luk, similarly when an affix is elided by using the terms slu or lup, the disappearance gets the name of slu or lup.
Thus in अद् + शप्लुक् + ति = अत्ति 'he eats.' Here the vikarana शप् has been elided by using the word luk 2.4.72. Similarly in जुहोति 'he invokes,' the vikarana शप् is elided by the word slu 2.4.75, so in वरणाः 'a city in the vicinity of weeds called varana.' Here the Taddhita affix indicating vicinity has been elided by the word lup. 4.2.82.
Why do we use the words \of the affix\? Without these words, the sutra would have run thus:- \The disappearance is called luk, slu or lup.\ So that the disappearance of a base would also be caused by the use of these terms. Thus in 2.4.70, there would have been 'luk' of the bases agastya, and kaundinya; which however is not intended. In that sutra, the 'luk' of the affixes is only intended. So also in sutra 4.3.168 there would have been the substitution of 'luk' for the bases of the words.,