Prototype effects in discourse and the synonymy issue: Two Lakota postpositions*

Despite of being fully synonymous at the semantic level, the postpositions él ‘locative/directional’ and ektá ‘locative/directional’ in Lakota (Siouan, Central North America) display different semantic cores in discourse: the semantic prototype for él is the role of locative, while the semantic prototype for ektá is the role of directional. Both the functional synonymy between él and ektá and the observed prototype effects can be attributed to constellations created by grammaticalization processes: when an innovative grammatical element is developing—in this case, ektá—replacement of a functionally equivalent older element—in this case, él—is unlikely to happen overnight, so that the innovative and the older element can be expected to coexist for a while, and to share functional domains.