Which characteristic typically defines the start of puberty in females?

The onset of puberty in females is typically marked by breast development, which is the first physical sign that signifies the body is entering this developmental phase. This change is triggered by hormonal shifts in the body, particularly an increase in estrogen production, which influences the growth of breast tissue. While other changes, such as the development of pubic hair and height increases, also occur during puberty, they usually follow breast development or occur concurrently but are not the defining characteristic that marks the beginning of this stage. Menstruation is another important milestone, but it occurs later in puberty, typically after breast development has started. Therefore, breast development is recognized as the earliest and most significant indicator of the initiation of puberty in females.