Penal colonies refer to places where convicted criminals are sent to serve their sentences. However, there are different words that can be used as synonyms for the term. One of these is "prison colonies," which means a place where prisoners are held in captivity. Another synonym for the term is "convict colonies," which refers to a penal settlement established to move convicted criminals from their home country. The term "exile colonies" can also be used as a synonym, which means a place of banishment or confinement for prisoners or political dissidents. In summary, all these synonymous terms refer to facilities that hold prisoners and are often used interchangeably.