Most of the words in English are just quicker ways to express things that otherwise needs many words to describe. So, what is the minimum number of words or smallest dictionary that one can use to describe any thought they have? I have looked into Charles Kay Ogden's Basic English. But, I also read that many linguists do not like the word choices of Basic English (Why?)
I don't like it because there's no word for giraffe, salmon, reindeer, four or angstrom. I tried a few two- or three-word expressions that might describe giraffe, but there was nothing satisfactory. It is so much simpler to just add a word "giraffe", but that apparently violates a rule of the system that the lexicon is completely closed – a very unnatural state of affairs for a language, or for human cognition. It's not just that there are many words needed to describe giraffe, it's that there is a conventionalized and precise description available in that one word. Please don't get me started on numbers.
The more important question is, why would one do this in the first place? You only need 26 "words", – a, b, c, d...z and with combinations of those "words" you can form any existing English word (and a number that don't exist). True, the semantics of this much "simpler" system is worse than the semantics of Ogden's simplified system, but isn't the goal to reduce the size of the lexicon at the expense of all else? However, if the goal is simply to identify the most useful 850 words to know if you're learning English, it's not so bad, but still there are a bunch of words that you need to know, like "police, arrest, court, jail".