Ļ countability桼åɶ(桼åɴؤŬѤǤ)Ƥ룲ĤξΤȤزĻ٤Ȥ ʤ桼åɶ֤ϣĤξ(Ļ)ΤĤƤ롣 裱Ļ first countability axiom\((,\cal U)\) ˤĤơǤդ a Ф a ޤढĻĤγ² \(\{_{n};n1,2,\}\) Ŭ֤ȡa ޤǤդγ \(_{n}\) ޤȤ \((,\cal U)\) 裱Ļ(first countability axiom)Ȥ Ĥޤꡢ裱ĻȤϡ֤ǤդϲĻͤζɽĤȤ̣롣 褬裱ĻʤСϢ³Ϣ³פȤʤ롣 裲Ļ second countability axiomĻĤ \(\cal U\) ʬ \(\cal U_{0}\) ¸ߤǤդ \( \in \cal U\) \(\cal U_{0}\) θ½Ȥ \((,\cal U)\) ɽȤΰ \((,\cal U)\) 裲Ļ(second countability axiom)Ȥ Ĥޤꡢ裲ĻȤϡ֤ĻͤδĤȤ̣롣 ֤裲ĻʤСΰ֤裱Ļ interior point\( \subset \) ΤȤ\(a \in \) ޤ೫ \( \in \) ʤС a (interior point)ȤΤν ɽ롣 closure\( \subset \) ΤȤ\(a \in \) ޤ೫ \( \in \) ȤޤǾĽ(closure)Ȥ boundary\(\bar{A}\) ζ(boundary)Ȥ |