https://en.wikipedia.org/wiki/Natural_semantic_metalanguage
One thing that's confused me about this project is how much they are relying on people's prior human experience to understand the explications -- maybe a question of how much they use extensional or intensional definitions.
https://en.wikipedia.org/wiki/Extensional_and_intensional_de...
i wonder also how well you could get language primes to align with the axes of a word vector, as used in word2vec and other neural network based translation engines. what would a pure vector based language look like, I wonder?
This is related to what you wrote, "in practice, words are continually added to a language when new things need to be described". Consider new technologies for which new words are invented: these can generally be defined using the existing set of words in a language. The new word just provides a one- or two-word short form method of referring to that technology.
On the other hand, there are certain things - and I'm thinking specifically of human experiences as one set of those things - which are not easily summarized in a sentence and these get their own words. Consider emotions as one example. As the set of "known" human experiences (emotions, perspectives, etc.) grows, based on a more sophisticated understanding of human nature (via psychology, literature, etc.), new words are needed. Sometimes these words are borrowed from other languages, like "schadenfreude" and "empathy" (I was surprised to read that "empathy" first appeared in English in 1909, based on another German word).
On this basis, it would only be possible to limit the set of possible words if it were possible to limit the set of human experiences, which I don't think is possible. A transhuman/sci-fi example would be if a method was invented to perceive visual wavelengths that are currently outside the human visual spectrum as colours (i.e. infrared and ultraviolet, but perceived directly in the same way we perceive red and purple). I can't currently imagine a way (although perhaps there is one) of describing something like this using the existing set of words.
It is entertaining to look for corresponding patterns between formal languages (programming languages) and natural ones. For example, defining new words is essential and corresponds to procedures. What about templates/generics? I think the concept of adverbs and adjectives comes close. You take a generic word "car" and specialize it "blue car". Natural languages have namespaces, but they are implicit. A jaguar could be an animal or a car depending on context.
Maybe if there existed BF where you had a macro system for user-defined sequences, it would be possible to program in such a language.
I am not sure... in practice, words are continually added to a language when new things need to be described, although there was obviously a way to describe the thing before the new word came along..