The present article discusses the notion of variation in discourse as an essential characteristic of language and the linguistic parameters that can be used for its study. The article describes the different traditions in the study of variation and places special emphasis on the role of prosodic analysis in the study of spoken discourse. The study explores the use of discourse markers in the London-Lund Corpus and describes their linguistic variation by introducing the notion of APPROPRIATENESS. This notion, which combines the quantitative and qualitative presence of elements in discourse, is based on a mathematical index that can describe discourse variation with a sound systematic criterion.