The use of English to teach content subjects has been a growing trend in many parts of the world. It is labelled in a variety of ways, such as content-based learning, content and language integrated learning, immersion education, theme-based language teaching, and bilingual education, but it is referred to in this paper as English-medium instruction (EMI). The expansion of EMI worldwide has resulted in many different forms of EMI, as well as some confusion as to how they differ. In addition, a number of different forms of EMI may occur in the same school or institution, area, or country. The different forms of EMI can be usefully classified in the form of a typology. A typology provides a basis for objective and quantifiable accounts of the characteristics of EMI in different situations. The present typology describes 51 features across 10 curriculum categories, which were identified when comparing different forms and realizations of EMI. It highlights the many different dimensions of EMI that are involved in describing, planning, or evaluating EMI.