Devil & Demon

[Beswad]

What is the difference between the Devil and a Demon?

[NapoleonSolo]

There's only one Devil, there are many Demons

[andy hughes]

In the context iof 'The Devil' - the term usually refers to Lucifer / Satan, what ever incarnation of the force of evil you are naming. Some cultures refer to 'devils' as a catch-all label for any evil entities, as are 'demons'. so it's really just a matter of semantics.

[Octavius]

In Roman astronomy, Lucifer was the name given to the morning star (aka Venus). The morning star appears in the heavens just before dawn, heralding the rising sun. The name derives from the Latin term lucem ferre, "bringer, or bearer, of light"  the name was translated from the old Hebrew text which referred to a rather naughty king (Helal of Babylonia) who dressed in fine clothes and persecuted the Israelites.  Christian translations throughout the years have metamorphised the name Lucifer from 'son of the dawn' to mean, the fallen angel, the prince of darkness or satan.

Similarly, the Greek word for Satan (satanas) indicates an adversary, opponent, or enemy.  "Devil� came into English through the German language from the Greek word diabolos. Diabolos means a slanderer, treacherous informer and, traitor.  Demon: In old Greece, the word daim�n was often used in the meaning "the power controlling the destiny of individuals", "fate", "lot", "fortune". The verb daimonomache� meant something like "to fight against Heaven" (that is, against the divine powers).  Its all a matter of translation.

Generally speaking the devil is peoples personification of a single demon being - the devil is a demon, and a demon can take many forms.  Children can be little devils and a troubled mind can be full of demons.  It's also a matter of creed, but essentially they are the same thing as noted by the Catholic Encyclopedia:  

Demon: In Scripture and in Catholic theology this word has come to mean much the same as devil and denotes one of the evil spirits or fallen angels.

Devil: The name commonly given to the fallen angels, who are also known as demons.