What part of speech is the word supposed?

"Supposed" can be multiple parts of speech depending on how it's used in a sentence. Here are a few possibilities:

* Adjective: This is the most common use. "He's the supposed leader of the group."

* Verb: This is used in the past participle form. "I was supposed to be there at 6 pm."

* Past participle: Used as part of a verb phrase. "He had supposed that she was leaving."

Let me know the sentence you have in mind, and I can tell you exactly what part of speech "supposed" is in that context!