NEW CARDINAL FUNCTIONS RELATED TO ALMOST CLOSED SETS Cho, Myung Hyun; Moon, Mi Ae; Kim, Junhui;
In this paper, we strengthen the properties of approximation by points (AP) and weak approximation by points (WAP) considered by A. Pultr and A. Tozzi in 1993 to define -AP and -WAP for an infinite cardinal . We also strengthen the properties of radial and pseudoradial to define -radial and -pseudoradial for an infinite cardinal . These allow us to consider new cardinal functions related to almost closed sets; AP-number, WAP-number, radial number, and pseudoradial number. We study their properties and show the relationships between them. We also provide some examples around -AP and -WAP which are closely connected with -radial and -pseudoradial.