Adolescence (from Latin: adolescere meaning "to grow up") is a transitional stage of physical and mental human development generally occurring between puberty and legal adulthood (age of majority), but largely characterized as beginning and ending with the teenage stage. According to Erik Erikson's stages of human development, for example, a young adult is generally a person between the ages of 20 and 40, whereas an adolescent is a person between the ages of 13 and 19. Scholars have found it incredibly difficult to agree upon a precise definition of adolescence, because it can be approached from so many angles. A thorough understanding of adolescence in today’s society depends on information from various perspectives, most importantly from the areas of psychology, biology, history, sociology, education, and anthropology. Within all of these perspectives, it is safe to say that adolescence is viewed as a transitional period whose chief purpose is the preparation of children for adult roles. Historically, puberty has been heavily associated with teenagers and the onset of adolescent development. However, the start of puberty has had somewhat of an increase in preadolescence (particularly females, as seen with early and precocious puberty), and adolescence has had an occasional extension beyond the teenage years (typically males) compared to previous generations.