A bachelor is a man who has not been married and is not cohabiting. He lives on his own or with a flatmate/housemate. A woman in this situation is sometimes known as a bachelorette. A bachelor cannot have been married, as a man who married but then divorced is called a divorcé. A man whose wife is dead is a widower.
Sometimes, when a bachelor is going to be married, a bachelor party is organized to celebrate the last day that the person will be a bachelor for.