In the phrase fiesta de quince años, años means years.
Together, quince años means fifteen years, which refers to the milestone commemorated by the celebration. The tilde over the ñ is important in Spanish spelling: años means years, while anos without the tilde is a different and inappropriate word.
The phrase illustrates how the event’s Spanish name directly describes its purpose. A quinceañera is not simply any birthday party; traditionally, it marks the completion of 15 years and the passage from childhood into a new stage of life.
Spanish-speaking communities use several names, including quinceañera, quince, and fiesta de quince años. The exact wording can vary by country and family. Modern celebrations may be religious or secular and can be elaborate formal events or smaller gatherings, but the reference to fifteen years remains the central linguistic idea.