Abstract
Let 2 < n < omega. We show that any n-modal logic between K-n and S5(n) is not axiomatizable by a set of modal formulas containing finitely many propositional formulas. This is proved algebraically by showing that the corresponding variety of modal algebras, namely, that of diagonal free cylindric algebras of dimension n (RDf(n)) has no equational axiomatization using finitely many variables.