Ṣīghatihi al-aṣliyyah: the form treated as original in the analysis.
Ilā ṣīghatin ukhrā: a different form reached from it.
Taḥqīqan aw taqdīran: the shift may be established as an actual formal alteration or posited in grammatical analysis.
Not every pair of differently shaped words is an instance of ʿadl. This is a technical cause established for particular classes of words.