What part of speech one?

"One" can be several parts of speech, depending on its use in a sentence. Here are the most common:

* Numeral: When it refers to the number 1, like in "I have one apple."

* Pronoun: When it refers to a singular person or thing previously mentioned, like in "I saw a cat, and it was one I had never seen before."

* Adjective: When it modifies a noun, often meaning "single" or "only," like in "I have one question."

* Indefinite pronoun: When it refers to any single person or thing, like in "One should always be kind."

To determine the part of speech of "one" in a specific sentence, you need to consider its role and function within the sentence.