Is incapable a prefix or root word?

"Incapable" is not a prefix or a root word. It's a complete word meaning "unable to do something."

Here's the breakdown:

* "In-" is a prefix meaning "not" or "the opposite of."

* "Capable" is a root word meaning "having the ability to do something."

Therefore, "incapable" is formed by combining the prefix "in-" with the root word "capable."