Change theory has increasingly become an area of scholarship in STEM education. While this area has traditionally been a topic for organizational psychology, business management, communication studies, and higher education, STEM education researchers are increasingly aware of the need to use formal theories to guide change efforts and research. Formal change theory encompasses our current research-based knowledge about how and why change occurs, and therefore, can guide the selection and design of promising interventions. Yet learning about and using theory is challenging because many of us have no formal training in this area and relevant scholarship comes from many different disciplines. Inconsistent terminology creates an additional barrier. Thus, this essay aims to contribute to a common lexicon in STEM higher educational change efforts by clearly distinguishing between formalized change theory, which emerges from research, and a theory of change, which guides the logic of a specific project. We also briefly review the current state of the field regarding the use of formal change theory and provide examples of how change theory has been used in biology education. Lastly, we offer practical guidance for researchers and change agents who wish to more intentionally and effectively use change theory in their work.