system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The difference between Miles and Nautical Miles and why we need two different measurements?
gpt
The mile traces its origins to the Roman Empire and was originally 1000 paces (2000 steps), hence its similarity to the Latin "Mille" for thousand.  When people went to the sea the need for a distance measurement of that scale still existed, but ships don't do much pacing so a different standard had to be used.  While it's hard for a ship to measure how far it's gone it is much easier to figure out how far north/south it presently is by looking at the sun or stars.  Thus, a definition for a roughly mile-length unit came to be--it is 1/60 of a degree along a meridian (north/south line).

More modern definitions have evolved from these original definitions, so a modern-day mile is 5,280 feet , while a modern-day nautical mile is 1.150779 miles exactly.