In mathematics, a subset B ⊆ A {\displaystyle B\subseteq A} of a preordered set {\displaystyle } is said to be cofinal or frequent in A {\displaystyle A} if for every a ∈ A, {\displaystyle a\in A,} it is possible to find an element b {\displaystyle b} in B {\displaystyle B} that is "larger than a {\displaystyle a} ". Wikipedia