Vassalage

A duke typically held his duchy as a vassal of a king or emperor, the duchy itself a fief granted and defended under the vassalage relationship.

Vassalage is the personal bond of loyalty and service at the core of feudalism; feudalism cannot function without the vassalage relationship between lord and vassal.

A knight typically held his status as a vassal, owing military service to a lord in exchange for land or maintenance under the vassalage relationship.

Vassalage organized the political and military obligations of the feudal order while manorialism organized its economic life on the same estates; the two systems operated together in medieval Europe.

Protectorate and vassalage are both asymmetric-sovereignty relationships in which a weaker polity submits to a stronger power protection or overlordship while retaining nominal internal rule.

Daimyo lords held their domains as vassals of the shogun under a formal vassalage relationship, owing military service and loyalty in exchange for confirmed authority over their territories.

Suzerainty and vassalage describe the same asymmetric political relationship from opposite ends, the suzerain holding overlordship over a subordinate vassal who retains internal autonomy while owing tribute or service.