Boundary (topology)
In topology and mathematics in general, the boundary of a subset S of a topological space X is the set of points which can be approached both from S and from the outside of S. More precisely, it is the set of points in the closure of S, not belonging to the interior of S. An element of the boundary of S is called a boundary point of S. Notations used for boundary of a set S include bd(S), fr(S), and ∂S. Some authors (for example Willard, in General Topology) use the term frontier, instead of boundary in an attempt to avoid confusion with the concept of boundary used in algebraic topology and manifold theory.
A connected component of the boundary of S is called a boundary component of S.
Read more about Boundary (topology): Common Definitions, Examples, Properties, Boundary of A Boundary
Famous quotes containing the word boundary:
“Setting limits gives your child something to define himself against. If you are able to set limits without being overly intrusive or controlling, you’ll be providing him with a firm boundary against which he can test his own ideas.”
—Stanley I. Greenspan (20th century)