What part of speech is zero?

"Zero" can function as several parts of speech, depending on its context:

* Noun: When it refers to the number itself. Example: "Zero is the smallest non-negative integer."

* Adjective: When it describes a quantity or amount. Example: "The score was zero to zero."

* Adverb: When it modifies a verb, adjective, or another adverb to indicate a lack of something. Example: "He missed the target by zero inches."

So, the specific part of speech depends on how "zero" is used in a sentence.