What is the central birthday milestone celebrated by a quinceañera called in English?

In English, the central milestone of a quinceañera is a girl’s fifteenth birthday.

The celebration is not simply any birthday party: it traditionally marks the transition from childhood toward young womanhood. Families may express that transition through a formal gown, public presentation, symbolic gifts, dancing, and words from parents or relatives.

The tradition does not mean that every fifteen-year-old has the same responsibilities or legal status. Ideas about maturity, family duty, and adulthood vary among cultures and generations. Modern quinceañeras can also be personalized, with secular ceremonies, themed receptions, smaller gatherings, or celebrations held on a nearby date.

The birthday connection explains why the event is usually planned around the celebrant’s fifteenth year. It also distinguishes the tradition from a Sweet Sixteen party, which is a separate birthday custom most strongly associated with the United States and Canada.