Are Demon and Devil the Same?

A demon is any of the many angels that fell from heaven. The devil is a specific one of the fallen angels. The devil is a term used to refer to the one who is considered the leader or chief of the fallen angels. The devil is also known as Satan or Lucifer. Sometimes the plural (devils) is used interchangeably with demons, but when used in the singular, it refers only to the chief fallen angel.