👉 The term "complementoid" is a mathematical concept in topology, specifically in the field of algebraic topology. In this context, it refers to an object that can be considered as a subset of itself, but not all elements of the original set are included within its interior. Complementoids were introduced by Paul von Neumann and are named after him, who is also known for his work on the theory of complemented spaces. Complementoids have several properties in topology and algebraic geometry
