In the introduction to this special issue we consider the dynamics of language from three interrelated perspectives: ontogenesis, or the development of the language system in the individual; logogenesis, or the development of meanings across texts and discourses; and phylogenesis, or the changes to individual language systems over time. We discuss how these three methods of development are intrinsically connected, feeding into each other in such a way that they can be theorised as essentially different spatiotemporal perspectives on the same phenomenon. From there we pose three central questions for the modelling of change and contrast in Systemic Functional Linguistics (SFL), summarised briefly as: How can the theoretical and descriptive architecture of SFL be developed to account for the dynamics between these three genetic systems? How can we account for the expansion of the meaning potential of individual languages as a result of these processes? And to what extent are the fundamental categories of SFL adequate to the description of languages other than English and, hence, to the comparison of different languages? We then provide an overview of how the different papers in this special issue respond to these three questions.
