difference between robber, mugger, and thief

robber - (дээрэмчин, булаан дээрэмдэгч) хүч хэрэглэж авахад
a person who steals from a person or place, especially using violence or threats
mugger - (гудамжны дээрэмчин, гудамжний хулгайч) гудамжинд амьдардаг хулгайч
a person who threatens or attacks someone in order to steal their money, especially in a public place
thief - (хулгайч) нууцаар юм авах
a person who steals something from another person or place
   

difference between robber, mugger, and thief

• A mugger is someone who works in the street and uses force or the threat of force to steal money, mobile phones or whatever from people.
  
  A robber is a more general term and implies to me someone, or often one of a gang, who do things like rob banks, security vans etc (ie robbery is usually quite open and unsubtle). It can also be used as an alternative for brigand, bandit etc.
  
  A thief is to me more someone who takes things by stealth(нууцаар).
  
  Mugger does mean something specific, robber and thief are wider terms and in some cases can be used interchangeably.
• Okay, I'm going to take things from a legal point of view.
  Robber: Someone who steals something by using or threatening violence.
  Mugger (not a legal definition): This is more of a colloquial term - to me it suggets a theif who would "mug" or steal from someone in the street. It also suggests that they threaten or use violence.
  Stealer: I have never heard this said or used by native speakers.
  Thief: Someone who steals without using/threatening violence perhaps like a pickpocket.