In many circles, efforts are under way to develop definitions of college readiness, career readiness, or both. This brief contains a definition that is the culmination of 18 years of study and research on this topic. This definition, then, is based on both empirical evidence gathered via multiple research studies and on-the-ground interactions with practitioners attempting to improve programs that affect a wide range of students, particularly those who would be first in family to attend college. Postsecondary, in this definition, refers to any formal setting in which an individual pursues additional instruction beyond high school. This might include two- or four-year degree programs, certificate or licensure programs, apprenticeships, or training programs in the military. Furthermore, this definition differs from indices or "cut scores" that use a single cut score alone or in combination with another element, such as high school grade point average, to predict college success. This definition is designed to be actionable. It describes what students should know and be able to do in general terms that can then be defined and addressed with increasing detail and measured in a variety of ways using appropriately complex measures.