* As an ordinal number: "First" is an adjective when it describes the position of something in a sequence. For example, "the first day of school," "the first prize," "the first time I saw him."
* As an adverb: "First" can also be an adverb when it indicates order or priority. For example, "First, you need to gather your ingredients."
Let me know if you have a specific sentence in mind, and I can help you determine the part of speech of "first"!