These words all apply to a person who unlawfully takes property from another, but they have distinct meanings. A robber steals by the use of force or threat. A thief does his work in secret and by stealth. A burglar breaks and enters. Someone who takes your wallet while holding a knife in his hand is a robber, not a thief or a burglar. A person who lifts your wallet from the beach while you are swimming is a thief. An individual who forces open a window in your house and takes your wallet from the dresser is a burglar.
Dictionary of problem words and expressions. Harry Shaw. 1975.