1. Verb: When it means "to shorten" or "to reduce," it's a verb.
* Example: "The editor abridged the novel for a younger audience."
2. Noun: When it refers to a shortened version of something, especially a book or document, it's a noun.
* Example: "The abridged version of the book was much shorter than the original."
So, to determine the correct part of speech, you need to look at the context of how it's used in a sentence.