Kitāb al-ʿAyn
كتاب العين
al-Khalīl ibn Aḥmad, as transmitted by al-Layth ibn al-Muẓaffar · al-Khalīl d. 170 or 175 AH / 786 or 791 CE · Sound-ordered root dictionary
Instead of starting with alif, this dictionary starts with ʿayn, the sound its introduction places deepest in the throat, and files each root with every rearrangement of its letters found in use. It is the oldest surviving attempt to take in the whole Arabic vocabulary by a system. Reading it well takes two keys: the filing system, and an ear for the voices in it — al-Khalīl's, his transmitter al-Layth's, and later hands.
All the classical dictionaries