The River Acheron, also known as the River of Woe, is a prominent feature in Greek mythology and is often associated with the underworld. There are several synonyms for the word "River Acheron" that have been used over the years, including "Styx," "Cocytus," and "Lethe." Styx is thought to be the most well-known of these synonyms, as it is often used to describe the river that separates the living world from the underworld. The River Cocytus is another synonym that is mentioned in literature and is thought to represent the river of lamentation. Finally, the River Lethe is considered to be the river of forgetfulness and is often associated with the afterlife.