Life course theory, more commonly termed the life course perspective, refers to a multidisciplinary paradigm for the study of people's lives, structural contexts, and social change. This approach encompasses ideas and observations from an array of disciplines, notably history, sociology, demography, developmental psychology, biology, and economics. In particular, it directs attention to the powerful connection between individual lives and the historical and socioeconomic context in which these lives unfold. As a concept, a life course is defined as "a sequence of socially defined events and roles that the individual enacts over time" .These events and roles do not necessarily proceed in a given sequence, but rather constitute the sum total of the person's actual experience. Thus the concept of life course implies age-differentiated social phenomena distinct from uniform life-cycle stages and the life span. Life span refers to duration of life and characteristics that are closely related to age but that vary little across time and place.The family is perceived as a micro social group within a macro social context—a "collection of individuals with shared history who interact within ever-changing social contexts across ever increasing time and space" Aging and developmental change, therefore, are continuous processes that are experienced throughout life. As such, the life course reflects the intersection of social and historical factors with personal biography and development within which the study of family life and social change can ensue .
Several fundamental principles characterize the life course approach. They include: (1) socio-historical and geographical location; (2) timing of lives; (3) heterogeneity or variability; (4) "linked lives" and social ties to others; (5) human agency and personal control; and (6) how the past shapes the future. Each of these tenets will be described and key concepts will be highlighted. An individual's own developmental path is embedded in and transformed by conditions and events occurring during the historical period and geographical location in which the person lives. For example, geopolitical events (e.g., war), economic cycles (e.g., recessions), and social and cultural ideologies (e.g., patriarchy) can shape people's perceptions and choices and alter the course of human development. Thus, behavior and decisions do not occur in a vacuum, because people and families interact within sociohistorical time. Indeed, an understanding of the location of various cohorts in their respective historical contexts aids scholars and policy makers to identity circumstances that have differentially affected people's respective life histories.