  We introduce and study a class of betweenness algebras-Boolean algebras with
binary operators, closely related to ternary frames with a betweenness
relation. From various axioms for betweenness, we chose those that are most
common, which makes our work applicable to a wide range of betweenness
structures studied in the literature. On the algebraic side, we work with two
operators of possibility and of suffciency.
