Einfalt, dobra, uniplex, fold, single fold, pli

The word identifies the simplicity of naivete, guilelessness. The Einfalt is not   "complex," though the English language does not have a word like "uniplex," which is what the literal sense of the word leads us to think. It is the simplicity of a fold. Earlier translations elided the distinction between Einfalt and Einfach in Heidegger’s work. Where the difference was remarked, it was often explained with the emphasis on the Ein as "simple oneness." This attributes too much weight to the unifying force of the Ein, while Heidegger’s emphasis here falls much more on the "fold." The term itself emerges in the text   in response to an act of folding: the four are "folded into a single fourfold [in ein einziges Geviert   eingefaltet]" (GA79  : 12/11). The very next sentence then introduces the "single fold of the four [die Einfalt der Vier]" (GA79:12/11). This single fold names the simple belonging together of the four. (GA79: Translator’s Foreword)

simplicidade
simplicidade de conjunção
dobra do simples