(Semantic) definiteness means that an expression is morphosyntactically marked as hearer-known (definite or pronominal) and the hearer can infer exactly one entity to which this description applies at the current point in discourse, either because it is unique (Russel 1937), or it is the most salient entity in the current situation to which the referring expression may apply (Lewis 1979, v. Heusinger 1996). In particular, most pronuns are also definite as they refer to one particular antecedent.