Quinceañera is the Spanish feminine term for the fifteenth-birthday celebrant.
The same word is also widely used for the celebration itself, so context determines whether it means the young woman or the event. In Spanish, the feminine ending distinguishes quinceañera from quinceañero, the masculine form.
The term is related to quince, meaning fifteen, and to año, meaning year. The ñ and the accent are part of the standard spelling: quinceañera. English-language usage often retains the Spanish word because it names a cultural tradition with no exact one-word English equivalent.
Usage is not identical everywhere. Some communities use quinceañera primarily for the party, while others use it for the celebrant, and bilingual speakers may use both meanings in the same conversation.