What part of speech is leaving?

"Leaving" can be several parts of speech depending on its context:

* Verb: This is the most common use. Example: "He is leaving tomorrow."

* Gerund: A verb acting as a noun. Example: "Leaving early is a bad habit."

* Participle: A verb acting as an adjective. Example: "The leaving train was crowded."

To determine the part of speech, you need to look at the sentence and how the word is being used.