The original working definition of competency-based education was developed in 2011 at the National Summit for K-12 Competency-Based Education (Sturgis, Patrick, & Pittenger, 2011). The Summit was hosted by the Aurora Institute (formerly iNACOL) and the Council of Chief State School Officers, with more than 100 education innovators and practitioners attending. Eight years after creating the original working definition, feedback from across the field indicates that it should be updated to reflect a deeper understanding of key issues and developments in the field. This report presents the new definition, which was developed with extensive input from invited attendees at the second National Summit on K-12 Competency-Based Education in 2017 and from a technical advisory group of more than 40 experts and leaders in the field. The report also includes a set of belief statements, answers to frequently asked questions, and a brief discussion of common misconceptions about competency-based education. These provide essential context for understanding the definition and the field in which it is situated. Finally, resources are provided for further exploration of competency-based education policies and practices.