David Alan Black, Greek professor and author of a number of books on languages, suggests you don’t use Greek from the pulpit.
Speak emancipating truth in a way that all can understand, and we will thank you for it.Dave Black Online
I agree, and add the fact that in most cases when I’ve heard Greek referenced from the pulpit it is referenced incorrectly. Use your Greek or Hebrew to enhance your own study, but bring it to the people in their language.
I confess that I usually do use a Greek word (one, unless it’s in a language context), because people expect it of someone whose degrees are in biblical languages and not in theology. But I introduce it with a caveat, and tell people why I’m doing it.
Then again, I’m usually teaching small groups and only rarely preaching.