Biblically speaking, a demon is an 'unclean' spirit that follows (or obeys) Satan and not God. They are also called 'evil' spirits (Acts 19:12-16).
- Mark 1:24-27; 5:2-3; 7:25; 9:25; Acts 5:16; 8:7; Rev. 16:13.
- Clinton Arnold,
Powers of Darkness: Principalities & Powers in Paul's Letters. Downers Grove: IVP, 1992.