A rabbi is a person that ….

Every now and then an issue arises and people start arguing about whether we should call someone Rabbi Someone, “Rabbi” Someone, or just Someone. So, here’s the question – what’s a reasonable way to define rabbi? Only someone that knows kol hatorah kulah (your shul rav probably won’t make the cut), knows yoreh deah (maybe your rosh yeshiva wouldn’t even make it), has learned seriously for 10+ years? knows at least chumash, rashi, and most important sugyas, but it’s ok if he doesn’t know kodshim and zraim? or taharose?

I’ve people write things like, well he doesn’t know all of shas, or something like that, but by that standard, there are many frum “Rabbis” that we could probably agree are not actually rabbis. I have certainly met many unquestionably frum rabbis that wouldn’t know the difference between brachose and bechorose (and bikurim). Or wouldn’t be able to tell the difference between a mechilta and medrash rabbah.