Ancient uji were peer groups of many families joined by blood relationships or blood consciousness, and the head of a powerful family became the head of the uji and occupied a position similar to the head of a clan.
古代のウジは、血縁関係ないし血縁意識によって結ばれた多くの家よりなる同族集団で、有力家族の長が氏上（うじのかみ、うじがみ）となり、族長的な地位に立っていた。