posted by Avery .
In the sentence "On track and field day, the teacher was very proficient at announcing the events", is the word "proficient" a noun or verb?
Neither. "Proficient" is an adjective, describing teacher. He was a proficient teacher.
A quick way to determine a word's part of speech is to look it up in a dictionary. Find the definition and part of speech that seems to fit in your sentence. Usually, dictionaries have a sentence to show how the word is used.
I usually use http://dictionary.reference.com/