Adolescence is a transitional stage of physical and psychological human development that generally occurs during the period from puberty to legal adulthood (age of majority). The period of adolescence is most closely associated with the teenage years, though its physical, psychological and cultural expressions may begin earlier and end later. For example, although puberty has been historically associated with the onset of adolescent development, it now typically begins prior to the teenage years and there has been a normative shift of it occurring in preadolescence, particularly in females (see precocious puberty). Physical growth, as distinct from puberty (particularly in males), and cognitive development generally seen in adolescence, can also extend into the early twenties. Thus chronological age provides only a rough marker of adolescence, and scholars have found it difficult to agree upon a precise definition of adolescence.