Usually taken to refer to the transition to adulthood but argues that adulthood increasingly extends across a long period of the life course. (Brannen)
“Usually refers to the transition to adulthood and occurs when ‘young people are not dependent upon parental support, have life styles that we associate with the notion of ‘young adulthood’.” (Nilsen, Brannen, 2002)

As defined by author Julia Brannen. Young Europeans: Futures in transition. London: ESA/Routledge.