User:IssaRice/Adherent point and limit point

Let $(X,d)$ be a metric space, let $E$ be a subset of $X$, and let $x_{0}\in X$ be a point.

• there exists a sequence $(x_{n})_{n=1}^{\infty }$ of points in $E$ which converges to $x_{0}$
• for every radius $r>0$ the ball $B(x_{0},r)$ has nonempty intersection with $E$
• $x_{0}$ is an interior point of $E$ or is a boundary point of $E$
• for every open set $U$ such that $x\in U$ one has $U\cap A\neq \emptyset$
• for every open set $U$ such that $x\in U$ there is some $y\in U\cap A$ such that $y\neq x$
• for every open set $U$ such that $x\in U$, the set $U\cap A$ has infinitely many points
• there exists a sequence $(x_{n})_{n=1}^{\infty }$ of distinct points in $E$ which converges to $x_{0}$
• there exists a sequence $(x_{n})_{n=1}^{\infty }$ of points in $E$, none of which are equal to $x_{0}$, which converges to $x_{0}$