What part of speech is rebuilding?

"Rebuilding" can be a few different parts of speech, depending on how it's used in a sentence:

* Verb: This is the most common use. It describes the action of building something again.

* Example: "They are rebuilding the old bridge."

* Gerund: This is a verb form ending in "-ing" that acts as a noun.

* Example: "Rebuilding the city will take years."

* Present Participle: This is a verb form ending in "-ing" that modifies a noun or pronoun.

* Example: "The rebuilding process is slow and difficult."

So, to determine the part of speech of "rebuilding," you need to look at its function in the sentence.