This chapter proposes the difference between history discourse in classrooms and history discourse in textbooks, with a focus on knowledge structure. B. Bernstein distinguished two forms of discourse: horizontal discourse and vertical discourse. The class being examined is an English-medium instruction class at the tertiary level in a Chinese university. The chapter explores the effect of mode on language by comparing two versions of languages employed to construct historical knowledge of the same topic. In systemic functional linguistics, both language and social context are modeled as semiotic systems connected by a relationship of realization. Based on J. R. Martin's analysis of knowledge structure in the framework of field, H. Yu demonstrated how to study different knowledge structures in terms of taxonomic relation, nuclear relation, and activity sequence. The chapter aims to follow Yu's analysis of different knowledge structures and is largely inspired by the field perspective on the study of knowledge structure.