فَصْلٌ فِي المُعَرِّفِ وَأَقْسامِهِ
مُعَرِّفُ الشَّيْءِ ما يُقالُ لِإِفادَةِ تَصَوُّرِهِ، فَيُشْتَرَطُ أَنْ يَكُونَ مُساوِيًا أَجْلَى، فَلا يَصِحُّ التَّعْرِيفُ بِالأَعَمِّ وَالأَخَصِّ، وَالمُساوِي مَعْرِفَةً وَالأَخْفَى. وَالتَّعْرِيفُ بِالفَصْلِ القَرِيبِ حَدٌّ، وَبِالخاصَّةِ رَسْمٌ، فَإِنْ كانَ مَعَ الجِنْسِ القَرِيبِ فَتامٌّ، وَإِلّا فَناقِصٌ، وَلَمْ يَعْتَبِرُوا التَّعْرِيفَ بِالعَرَضِ العامِّ، وَقَدْ أُجِيزَ فِي النّاقِصِ أَنْ يَكُونَ أَعَمَّ كَاللَّفْظِيِّ، وَهُوَ ما يُقْصَدُ بِهِ تَفْسِيرُ مَدْلُولِ اللَّفْظِ.
The definer of a thing is what is said in order to give a of it. So it must be equal to it and clearer: defining by the more general or the more is not sound, nor by what is equal in being known, nor by the more obscure. by the near is a real definition (ḥadd), and by the property a description (rasm); with the near they are complete, otherwise incomplete. They did not take account of defining by the . In the incomplete kind it has been allowed to be more general, like the verbal definition, which is meant to explain what an signifies.
Tahdhīb al-manṭiq · p. 7