Expounding knowledge through explanations: Generic types and rhetorical-relational patterns

In this paper, we focus on contexts where the primary activity is to expound knowledge about general classes of phenomena, either by categorizing and characterizing them or by explaining them based on some theory, ranging from a commonsense folk theory to an uncommonsense scientific theory. Texts produced in such contexts include science lectures, research articles, and entries in encyclopedias. We focus on explanations, considering them across strata in terms of context, semantics, and lexicogrammar, and summarizing contributions from different research strands. Against this background, we report on a study of the registers used in secondary school chemistry textbooks in Hong Kong. We begin by summarizing a framework for classifying the contexts in which texts operate - a framework designed to allow us to differentiate different kinds of text according to the contexts they operate in. Then, we focus on one type of context - that of expounding knowledge about general classes of phenomena. Next, we identify different strategies of expounding knowledge, contrasting explanations and categorizations, and then discuss explanations in more detail. Finally, we move to the question of how these contextual types are realized semantically as texts organized as rhetorical complexes, drawing on secondary school textbooks in chemistry in particular.