Definition of lethal

The word "lethal" derives from the Greek word "λεθαλός" (lethalous), which means "causing death". The prefix "leth-(a)" in Greek was used to indicate death, and it is believed to be derived from "lethes", which translates to "forgetfulness" or "oblivion". In ancient Greek mythology, Lethe was one of the five rivers that formed the underworld river Styx. It was said that those who drank from Lethe would forget their past and lose their personal identity, essentially dying in a way that was both spiritual and symbolic. As the word "lethal" maintains its root in the Greek word "lethalous", it is evident that its arcane origins lie in the mythos and folklore of ancient Greece. Over time, the word was adopted into Latin, Old French, and Middle English, ultimately evolving into its modern usage in English as an adjective describing things or substances that have the power to cause death, such as poison or disease.