In this paper I argue that the definiteness marking function of the possessive suffix of some Uralic languages is not the outcome of a grammaticalization pathway but has always been inherent to them. The possessive suffix has thus two main functions: establishing a relation between entities or a relation between an entity and the discourse and indicating the definiteness of the referent of the marked noun. The interpretation of the suffix as a marker of definiteness or a marker of possession depends on the conceptual noun type of the marked noun and on the context.