FIGURE 1. The glossogenetic tree of Indo-European language.

The words of language are not inherited biologically, but are passed on culturally through learning. This process of 'cultural evolution' generates a hierarchical tree of relationships among languages, here illustrated by the Indo-European family. Just as descent with modification in biological evolution (phylogeny) leads to phylogenetic trees, so the analogous process in language change (glossogeny) can lead to glossogenetic trees.