* Verb (past participle): This is the most common usage. "Plunged" indicates a past action of forcefully pushing or thrusting something into something else, often with a feeling of suddenness or depth.
* Example: "The ship plunged into the depths of the ocean."
* Adjective: This usage is less common, but "plunged" can describe a state of being immersed or deeply involved in something.
* Example: "He was plunged into despair after losing his job."
To determine the correct part of speech, you need to look at how the word is used in the specific sentence.