It kind of is a proof if we assume that single words can be translated at all. Translate a single word from Language X (more words) to language Y (fewer words) and back. I can't uniquely recover all the words in Language X that way.
I don't know about that. For many practical purposes probably not?
I'm just on the thread following this idea: "The article seems to think that a word is untranslateable if there is no single word in the target language"
So we're talking about "translatability" of single words. Mapping multiple words of language X to one word of language Y is going to have some effect on translation.
