What term describes a person loyal to a lord in the feudal system?

The term that describes a person loyal to a lord in the feudal system is "vassal." In the context of feudalism, a vassal is someone who has entered into a formal agreement with a lord, receiving land or protection in exchange for loyalty and service, often including military support. This relationship formed the basis of the feudal hierarchy, where loyalty and mutual obligations were paramount.

While the other terms relate to roles within the feudal system, they serve different functions. A serf is typically bound to the land and works for the lord, but does not share the same level of loyalty or land ownership as a vassal. A baron is a title that designates a nobleman and may be a lord themselves but is not synonymous with the loyalty aspect of the vassal-lord relationship. A knight is often a vassal who has received land (a fief) and serves as a mounted warrior; however, the term "knight" specifically refers to their warrior status rather than the loyalty aspect that defines a vassal's role. Therefore, "vassal" accurately encapsulates the relationship of loyalty to a lord in the feudal system.