* Prefix: There isn't a true prefix in "underground."
* Root Word: The root word is "ground," meaning the surface of the earth.
* Suffix: The suffix is "-under," which indicates a position below or beneath something.
It's important to note that while "under" is a common prefix, in this case, it functions more like a prepositional phrase modifying the root word "ground."
Therefore, "underground" doesn't have a traditional prefix, but instead uses a prepositional phrase to express its meaning.