* Adjective: This is the most common use. It describes a noun.
* Example: "She had a successful career."
* Noun: This is less common, but it can be used to refer to something that is successful.
* Example: "The project was a huge success." (Here, "success" is a noun, and "successful" is an adjective describing it).
* Verb: It can also be a verb, meaning "to achieve success." This is less common in everyday language and is more often found in formal writing.
* Example: "She successfully navigated the complex situation."
So, the part of speech of "successful" depends on how it is used in the sentence.