@uses of cases in sUtras

In the /pANini sUtras, the cases are sometimes used in special senses. These special meanings are used also in the commentaries, but not in ordinary Sanskrit.

The third can mean 'near'.
The fifth can mean 'after' (by tasmAdityutt...).
The sixth can mean 'instead of' (by SaSThIsthAney...).
The seventh can mean 'before' (by tasminnitin...).
The seventh can also express "when meaning", "in the sense of". So the word adhikArtha-vacane अधिकार्थॱवचने in sUtra kRtyairadhik... translates to "when the meaning is an adhikArthavacana अधिकार्थवचन (exaggeration)".

Some examples —

When we apply rule stozzcunAzcuH to rAjnas राज्नस्, the rule says literally —

"with j ज्, instead of n न् there is J ञ्".

This "with j ज्" (third case) means that the change happens when n न् is either before j ज् or after j ज्. Here the third case means "near", not "with" as usually. this is done because saying scunA स्चुना "with a scu" is shorter than using proper Sanskrit for "near a scu स्चु", which would be scos samIpe स्चोः समीपे.

Now, rule AdguNaH when aplied to atra अत्र + indraH इन्द्रः literally says something roughly like —

"from a अ replace i इ with e ए and delete the a अ"

Rule tasmAdityutt... allows the word At आत् "from a अ A आ" to mean "after a अ". Again this is done because the proper way of saying "after a अ A आ" is too long — asya param अस्य परम्.

Rule torli, when applied to tat तत् + laghu लघु, literally says

"of t त् in l ल् there is l ल्".

Yet, rule SaSThIsthAney... teaches that an "of t त्" in a sUtra may mean "instead of t त्".

Then rule tasminnitin... says that "in l ल्" in a sUtra may mean "before l ल्". So the true meaning of torli is —

"instead of t त् before l ल् there is l ल्".