* Verb (past participle): This is the most common use. It describes an action that has already happened, for example, "She expressed her gratitude."
* Adjective: It can describe something that has been made clear or stated, for example, "His feelings were expressed in a letter."
* Noun: Less common, but it can refer to an emotion or opinion that is made known, for example, "His expressed opinions were controversial."
To determine the part of speech, you need to look at the sentence it's used in and see how it functions grammatically.