quiditas

• quidditās

From quid (“what”) +‎ -tās (“ness”).

• (Classical) IPA^(key): /ˈkʷi.di.taːs/, [ˈkʷɪd̪ɪt̪äːs̠]
• (modern Italianate Ecclesiastical) IPA^(key): /ˈkwi.di.tas/, [ˈkwiːd̪it̪äs]

quiditās f (genitive quiditātis); third declension

1. (Medieval Latin) quiddity, whatness
   • c. 1250, Thomas Aquinas, chapter 4, in Dē ente et essentiā:

     Omnis autem essentia vel quiditās potest intelligī sine hōc, quod aliquid intelligātur dē esse suō; possum enim intelligere quid est homō vel phoenīx et tamen ignōrāre an esse habeat in rērum nātūrā.

     But every essence or quiddity can be understood without anything being understood about its existence; for I can understand what a man is, or a phoenix, and yet not know whether it has existence in the nature of things.

Third-declension noun.