👉 Projectivity is a mathematical concept that refers to a property of a function or a set of functions such that every point in its domain has an open neighborhood whose closure is also contained within the domain. This means that for any point x in the domain, there exists a neighborhood U containing x that contains all points in the range of the function at least as far away from x as possible. In other words, projectivity ensures that the set of points where the function takes on values is a closed and
