As the global economy transforms into a knowledge-based society with an enhanced focus on information and innovation, success will depend on the ability of global citizens to work effectively with knowledge and technology (Drucker, 1993; Sawyer, 2006; Schwab, 2017). Working effectively with knowledge and technology requires thinking critically and creatively, solving problems collaboratively, using technology effectively, and understanding our capabilities as lifelong learners. These skills are referred to as 21st-century skills or crosscutting capabilities (CCCs). The inclusion of these skills in the classroom requires the ability to continue to effectively define, teach, and measure these skills in a way that will allow us to track, cultivate, and share student proficiency. Defining and organizing the CCCs so they can be taught and measured is a critical first step that drives the design and development of learning and measurement tools. This paper provides ACT's construct definitions for these skills based on prior research, including research into how individuals use these skills in applied settings. It also provides an overview of the value and application of these skills in academic and workforce settings. [For "Beyond Academics: A Holistic Framework for Enhancing Education and Workplace Success. ACT Research Report Series. 2015 (4)," see ED558040.]