The Spanish word pronounced approximately “KEEN-say” is quince, meaning “fifteen.”
Quince is the numerical foundation of quinceañera, the name for a traditional fifteenth-birthday celebration. In standard Spanish pronunciation, the c before e is pronounced like s in much of Latin America and like th in much of Spain, so pronunciation varies by region.
The neighboring number catorce means fourteen, while dieciséis means sixteen. Those distinctions matter because the tradition is specifically associated with the fifteenth birthday, not simply with adolescence in general.
English speakers often recognize quince through the celebration’s name but may not know its literal meaning. Learning the number also helps explain related Spanish expressions and why the celebration’s symbols frequently use groups of 15.