* Adjective: This is the most common usage, describing something that is likely to cause disagreement or argument.
* Example: "The new policy is a controversial one."
* Noun: "Controversial" can also be a noun, referring to something that is likely to cause debate.
* Example: "The issue of gun control is a controversial."
* Adverb: While less common, "controversially" can be used as an adverb to describe how something is done.
* Example: "The politician controversially refused to answer the question."
The specific part of speech depends on its context within a sentence.