variable

The word 'variable' originates from the Latin verb variare, meaning "to change, to make different," which itself derives from the adjective varius (varied, diverse). The suffix -abilis, indicating capability, was attached to form the Late Latin variabilis, meaning "changeable." This term was adopted into Middle English via Old French, carrying the sense of "liable to change." The logical progression from the literal root "to change" to the modern abstract meanings—describing something inconstant or a mathematical quantity that can assume different values—is direct, with the suffix "-able" clearly marking its adjectival function of expressing capacity.