1. A long-distance running race: This is the most common meaning, referring to a race of approximately 26.2 miles (42.195 kilometers).
2. Any prolonged or arduous task or activity: This meaning is metaphorical and derives from the original historical event. It's used to describe something that takes a lot of time, effort, and endurance.
Origin of the word:
The word "marathon" comes from the Battle of Marathon fought in ancient Greece in 490 BC. The legend says that a Greek soldier named Pheidippides ran from Marathon to Athens to announce the Greek victory over the Persians. He ran the entire distance, delivering the news, and then died from exhaustion.
This story was popularized in the 19th century, and the first modern marathon was held in 1896 as part of the first Olympic Games in Athens.