I have long wondered whether it would be possible to identify the most basic, core words of English, and construct a dictionary such that all definitions eventually reduce to those words. That way, a speaker of a foreign language could learn the meanings of the core words by translation into their native language, and then the process of learning a new word would be: look it up in the dictionary, and if there are any words in the definition that you don't already know, look those up, and so on until everything is reduced to the basic words you already know. The question then is, how many basic words must there be, and which ones are they? I realize nobody actually learns a language like this, but it's still conceptually interesting, analogous to the idealized process of reducing a mathematical proof all the way to the axioms (which, of course, mathematicians don't actually do, but in principle they could).