Boundary
# Definition
Let $X$ be a Topological Space and let $S \subset X$. Then the Boundary of $S$, denoted $\text{bd}S$, is the Set $$\text{bd}S := \text{cl} S \setminus \text{int} S.$$
Search
Let $X$ be a Topological Space and let $S \subset X$. Then the Boundary of $S$, denoted $\text{bd}S$, is the Set $$\text{bd}S := \text{cl} S \setminus \text{int} S.$$