The Most Frequent Words in a Language

i would imagine that it's very importantly the word, the actual words that students do know. What kind of words do you usually recommend for teachers to focus on when they're choosing what to teach students? Yes, that's a huge question. And it seems not easy teachers to wrap their heads around. So we want them to to be words that appear often enough that they're going to be useful. But not spend time teaching words that are either pretty easy and well known,. which are usually the most frequent.