The words needed to define a universal turing machine (and a program to simulate a human brain, but that doesn't require additional words). We could extend it

The words needed to define a universal turing machine (and a program to simulate a human brain, but that doesn't require additional words). We could extend it to cover words not conceivable by humans, and any universe, by using a program to simulate those, but (1) I assume the question implicitly assumes human words, though (2) it wouldn't require more words anyway.