I found this I wonder if 850 words really could be used to define all the others.

Do you mean like root latin words?

@LostInParadise English has four major word classes: nouns, verbs, adjectives and adverbs.

https://dictionary.cambridge.org/grammar/british-grammar/word-classes-and-phrase-classes

What I meant was this. If you look up a word in the dictionary, the definition is given in terms of other words. You can then look up the definition of those words. If you keep doing this, you will eventually end up in a loop. Suppose that the dictionary maker chose a group of words that were undefined but which defined, directly or indirectly, every other word in the dictionary. How many such words would we need, and what might some of them be.