«التَّعْبِيرِ عَنِ الْمُرَادِ تَأْدِيَةَ أَصْلِهِ بِلَفْظٍ مُسَاوٍ لَهُ»
Expressing the core intended meaning in wording proportionate to it.
«أَوْ بِلَفْظٍ نَاقِصٍ عَنْهُ وَافٍ بِهِ»
Or in fewer words, while still conveying it adequately.
«أَوْ بِلَفْظٍ زَائِدٍ عَلَيْهِ لِفَائِدَةٍ»
Or in additional wording that serves a benefit.
These yield, respectively, musāwāt, ījāz, and iṭnāb. The critical conditions are adequacy in concision and benefit in expansion.