What part of speech is thoughtful?

"Thoughtful" can be either an adjective or an adverb, depending on its function in a sentence.

As an adjective:

* It describes a noun, meaning "characterized by or given to thought": "He gave me a thoughtful gift." Here, "thoughtful" describes the noun "gift."

As an adverb:

* It modifies a verb, adjective, or another adverb, meaning "in a thoughtful manner": "She listened thoughtfully to his concerns." Here, "thoughtfully" modifies the verb "listened."