female spirits of justice and vengence. They were said to have been born from the blood of Uranus that fell on Gaia when Cronos castrated him - or according to another version they were the offspring of Nyx.
There are usually three of them: Alecto, Megaera and Tisiphone. They had the effect of sending their victims mad, hence their name, from furor, 'raving', 'madness'.
Cicero and others identified them with a somewhat obscure Roman goddess called Furina or Furrina, who was believed to have had a grove on the banks of the river Tiber in Rome and to have been a kind of goddess of the spring. The Greek name for the Furies was Erinyes.