[SOLVED] In API design, what is the term for entities that can vary without impacting each other?

There's a word that's used in API design that relates to the coupling between two entities. For example, suppose we have a class in a language such as C# (not important to the question) like:

  class Point
  {
    public int X;
    public int Y;
  }

The X and Y members of the class have this property: changing X does not cause a change in Y or vice-versa.

What is the word used to describe the property? I know I've seen it mentioned a lot in discussing the C++ standard library, but it doesn't seem to be used much in .NET circles.