* Adverb: This is the most common use. It describes how something is done, indicating movement over the edge of a vessel or a high place.
* Example: "The sailor accidentally fell overboard."
* Prepositional phrase: When used with "go" or "fall," it acts as a prepositional phrase indicating direction.
* Example: "The ship went overboard in the storm."
* Adjective: Less common, but possible, "overboard" can describe something that has gone over the side of a boat.
* Example: "The overboard cargo was lost at sea."
It's important to look at the context of the sentence to determine the specific part of speech.