What part of speech is vowed?

"Vowed" can be two different parts of speech depending on how it's used:

* Verb (past tense/past participle): When used as a verb, "vowed" describes a past action of making a solemn promise. For example: "She vowed to never betray her friend."

* Adjective: "Vowed" can also be used as an adjective meaning "promised or pledged". For example: "He was a vowed enemy of the king."

So, without context, you can't definitively say what part of speech "vowed" is. You need to look at the sentence it's in to determine its function.