Final answer:
The term for a screen separating the chancel or choir from the nave of a medieval church is a Rood screen. It is a key feature in many Gothic and Romanesque churches and contributes to the church's sacred architecture.
Step-by-step explanation:
The term used for a screen, often elaborately adorned and properly surmounted by a rood, that separates the chancel or choir from the nave of a medieval church is a Rood screen. These screens can be found in many Gothic and Romanesque churches, where they serve as a physical and symbolic barrier between the congregational area of the nave and the sacred space of the chancel.
The chancel itself is the space behind the altar of a church, which often contains the choir. Throughout different periods and architectural styles, such as Byzantine with the templon and Gothic with the use of tracery, these screens have evolved in design but retained their fundamental purpose. In Gothic architecture, for instance, tracery is a distinguishing feature, where stone is primarily used to form intricate patterns for stained glass windows.
Such artistic elements contribute to the overall architectural grandeur of medieval churches, integrating theology with visual arts to foster a sense of divine presence and communal worship.