of or like the social,
economic and political system in which lesser nobles, such as barons, are tenants on land owned by a
king. They provide military and other assistance to their
king in
return for his protection and the
use of the land. Part of the
use of the land includes the
use of the serfs (slaves) or peasants that live and
work on that land.
—9th ACC Volume 2 Approved Glossary