daemon

Daemon, daemonis is third declension masculine, a straight borrowing of Greek daimon, and the meaning shifted violently on the way in. For a Greek or a classical Latin writer a daemon is a divine power or a guiding spirit, morally neutral: the daemon of Socrates was the voice that warned him off. Apuleius can write about good daemones without irony.

Christian Latin closed that door. In the Vulgate and everything after it, daemon means an evil spirit and nothing else, which is why the word arrives in English as demon and takes daemonium, daemoniacus and energumen along with it. Two spelling notes: the ae is regularly flattened to e in medieval manuscripts, giving demon and demones, and the genitive plural daemonum is easy to misread as an accusative singular.