You only covered atoms, actually. Nouns are a union between an atom and an ordered pair of nouns, which means that they shaped like binary trees. A struct of `[

You only covered atoms, actually. Nouns are a union between an atom and an ordered pair of nouns, which means that they shaped like binary trees. A struct of `[a b c d]` is actually laid out as `[a [b [c d]]]`