What do we call a warrior on horseback in medieval Europe?

The story behind the answer

Unlike generic labels like “cavalryman” or “horseman,” this term denoted a legally recognized warrior elite: landholding vassals who fought as heavy cavalry and owed military service to a lord. Training began in childhood (page, squire) and culminated in a dubbing ceremony; equipment was costly—warhorse, mail and later plate armor, lance and sword—so the role was tied to wealth and status.

Their shock charges shaped battles from the Norman Conquest to the Crusades, and their behavior was ideally guided by chivalric codes of honor and piety. “Lancer” refers to a weapon specialty, whereas this title encompassed a full social and military role in feudal society.