* Noun: When referring to the fruit itself.
* Example: "I ate a juicy plum."
* Adjective: When describing something as excellent or superior.
* Example: "That was a plum job opportunity."
* Verb: In some dialects, "plum" can be used as a verb meaning "to plop down" or "to fall heavily."
* Example: (Informal) "He plum dropped his phone."
So, to determine the part of speech, you need to consider the context in which it's used.