Puberty is not a single event, but rather a complex metamorphosis. It is a cascade of changes that result in adult appearance, adult physiology, and altered identity. Although sexual dimorphism, differences in form and structure between males and females, are initiated at conception, some of the most salient biological differences between males and females emerge during pubertal transition. However, identifying exactly when puberty begins has been difficult. It is easier to know that puberty has already started than to pinpoint its exact onset, since the initiation of puberty is not completely understood.
As puberty is a process and not an event, its definition partly depends on the purpose for which the definition is being used. It is not necessary to measure hormones to define puberty if the purpose of the definition is to determine rate of growth. On the other hand, if an understanding of the interplay between different aspects of puberty is desired then the definition and measurement need to be more complex. In determining the source of the decrement in body image that many girls experience at puberty, to take one specific example, it may be best to measure multiple characteristics of puberty (increase in body fat, breast development, hormones, etc.), as well as the contextual factors in which these biological changes occur (degree of weight-related teasing by peers, media-induced culture of the thin ideal, parent preoccupation with body weight and shape, etc.).
Arguably, both the individual’s pubertal changes and the context in which these changes occur constitute the best definition of puberty for understanding issues such as body image change. In fact, it can be argued that a full understanding of most psychological aspects of puberty requires measuring both the individual pubertal changes and the environmental factors that give these changes meaning. In this view, the definition of puberty is “purpose dependent” and in its more complex form includes interrelated biological, psychological, and social factors.