A common extension of Lindel\"of, H-closed and ccc

Abstract

The inequality $|X| \leq 2^{\chi(X)}$ has been proved to be true for Lindel\"of spaces (Arhangel'ski\u\i, 1969), $H$-closed spaces (Dow-Porter, 1982) and ccc spaces (Hajnal-Ju\'asz 1967), by quite different arguments. We present a common extension of all these properties which allows us to give a unified proof of these three theorems.