This book brings together research from mathematics education and instructional design to describe the development and impact of online environments on prospective and practicing teachers’ learning to teach mathematics. The move to online learning has steadily increased over the past decade. Its most rapid movement occurring in 2020 with most instruction taking place remotely. Chapters in this book highlight issues related to teacher learning in three main contexts: formal, informal, and experiential or practice-based. This volume brings together researchers from the different but related...