Devil and Demon may have different etymologies in different languages, but in English- Devil almost exclusively refers to Satan or Shaitan of the Christian bible and Quran. Demon is more general- It refers to any malignant creature or spirit. Devil comes from the Greek word "Diavolos" which means "the accuser", Demon comes from the Greek word "Daimon" which can signify "spirit" or "departed souls".

I am the devil. Everyone who serves me is a demon.

the devil is the master of all demons ^^

devil is chaytan in arabic. demon is jan in arabic.

devil is demon's friend