The growth of online learning in the K-12 sector is occurring both remotely through virtual schools and on campuses through blended learning. In emerging fields, definitions are important because they create a shared language that enables people to talk about the new phenomena. The blended-learning taxonomy and definitions presented in this paper expand upon and refine the authors' previous work in helping to create a shared language for the K-12 blended-learning sector. In their report titled, "The rise of K-12 blended learning," the authors observed that there were six main blended-learning models emerging in the sector from the perspective of the student. This paper introduces a number of changes to that taxonomy based on feedback from the field and the need to update the research to keep pace with new innovations that are occurring in blended learning. Most importantly, the paper eliminates two of the six blended-learning models--Face-to-Face Driver and Online Lab--because they appear to duplicate other models and make the categorization scheme too rigid to accommodate the diversity of blended-learning models in practice. By moving from six to four overarching models, they have created more breathing room in the definitions. They hope these new models will better describe the majority of programs so that nearly all blended-learning programs will fit comfortably within one of the four. Notes about how this taxonomy differs from the taxonomy in "The rise of K-12 blended learning," January 2011 are appended. (Contains 12 figures and 16 notes.)