Effort is a widely used concept within educational research that blends a range of student behaviors focused on mastering a skill or completing a task. Despite its widespread use, few analyses clearly articulate, define, or embed effort in a distinctive theoretical framework. Consequently, there is little consensus on the operational definition of effort. Because there is not a well-established theoretical foundation with a corresponding empirical tradition, this chapter evaluates a disparate group of analyses that loosely use effort as a key construct. Given this paucity, we use this review to develop a typology to organize the various conceptions of effort. Unlike other noncognitive skills reviewed in this book, effort is mostly used as an outcome rather than a predictor. As such, this review emphasizes the measurement approaches used rather than predicative efficacy. We first discuss the methods used to select articles, followed by a discussion of the different conceptual dimensions identified in the articles. We then provide an overview of the measures used and their relationships with other constructs. We conclude with a discussion of the methodological implications for defining and using measures of effort.