The Finnic adposition and case system provide a limited empirical framework for the discussion of various synchronic expressions and diachronic processes in language. The following questions emerge from the data that illustrates the interaction between form and function in the Finnic adpositional phrases and case system: How should one account for the typological divergence between genetically related languages? Do diachronic processes transfer morphosyntactic properties or patterns and are they conditioned by endogenous or contact-induced innovations? What is the relationship between language-specific and more universal tendencies? These problems are discussed from the viewpoint of language typology, diachronic change and language contact.