What is the part of speech down?

"Down" can be several parts of speech, depending on how it's used in a sentence:

* Preposition: "The ball rolled down the hill."

* Adverb: "The sun went down."

* Adjective: "The down payment was high."

* Noun: "The bird flew in a downy swoop." (referring to a feather)

* Interjection: "Down, boy!"

To determine the part of speech, you need to look at its role in the sentence.