What part of speech is yesterday in the sentence leaves hung tree?

The word "yesterday" is not present in the sentence "leaves hung tree." This sentence is incomplete and doesn't make grammatical sense.

To determine the part of speech of "yesterday," we need a complete sentence.

Here's how we can analyze "yesterday" depending on its usage:

* As an adverb: If the sentence were "The leaves hung on the tree yesterday," then "yesterday" would be an adverb modifying the verb "hung" by indicating when the action took place.

* As a noun: In a sentence like "Yesterday was a beautiful day," "yesterday" would function as a noun, referring to the previous day.

Please provide a complete sentence so we can accurately identify the part of speech of "yesterday."