Origin: Germanic Old English prefix
Underworld has 4 different meanings across 1 category:
the criminal class
"The detective spent years undercover, infiltrating the underworld to dismantle the city's drug ring."
(religion) the world of the dead
"No one goes to Hades with all his immense wealth"
The world of the dead, located underneath the world of the living; the afterlife.
"The term is also commonly written as Underworld to match certain style guides."
Alternative letter-case form of underworld
In plain English: The underworld is the place where people believe dead souls go after they die.
"The detective spent years investigating crimes that took place in the underworld without ever being caught."
Usage: Use underworld to describe either the literal realm of the dead or metaphorically as the hidden criminal element within a city. Avoid confusing it with "underground," which refers specifically to physical subterranean spaces rather than supernatural realms or illicit activities.
The word underworld is formed by combining the prefix under with the noun world to describe a place beneath the earth's surface. This literal construction was first used in English during the late 16th century to refer to the realm of the dead or Hades.