THE MAIN DIVISIONS OF THE INDO-EUROPEAN GROUP In describing the historical development of a language group we have recourse to various metaphors and "models."
One such metaphor is that of the family, by which we speak of the Proto-Indo-European parent language with its various descendants. Another metaphor is the botanical one, by which we speak of the Indo­-European stem with its several branches. These two metaphors are often combined in a family-tree model of language.