Interested can be an adjective and a verb.
Adjective: Having or showing interest.
Verb: The past tense of the verb 'interest'.
It's an adjective.
The word 'in' would be a preposition in the example sentence you gave.
"Interested in" is a prepositional phrase typically used to indicate a preference or desire for something. It functions as an adjectival phrase modifying a noun or pronoun in a sentence.
The question "What part of speech is reputation?" means that someone is interested in knowing the part of speech (noun, verb, pronoun, adjective, adverb, preposition, conjunction, interjection) for the word reputation. Reputation is a noun.
The best speech for kids is, something that there interested in, "like to talk about".
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.
what part of speech is beneath
adverb
The part of speech for "explicit" is an adjective.
The part of speech for "lecturer" is a noun.