Demon \De"mon\, n. [F. d['e]mon, L. daemon a spirit, an evil spirit, fr. Gr. ? a divinity; of uncertain origin.]

1. (Gr. Antiq.) A spirit, or immaterial being, holding a middle place between men and deities in pagan mythology.

The demon kind is of an intermediate nature between the divine and the human. --Sydenham.

2. One's genius; a tutelary spirit or internal voice; as, the demon of Socrates. [Often written d[ae]mon.]

3. An evil spirit; a devil.

That same demon that hath gulled thee thus. --Shak.

Source: Webster's Revised Unabridged Dictionary (1913)