  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.
