Presbyterian (or presbyteral) polity is a method of church governance ("ecclesiastical polity") typified by the rule of assemblies of presbyters, or elders. Each local church is governed by a body of elected elders usually called the session or consistory, though other terms, such as church board, may apply. Groups of local churches are governed by a higher assembly of elders known as the presbytery or classis; presbyteries can be grouped into a synod, and presbyteries and synods nationwide often join together in a general assembly. Responsibility for conduct of church services is reserved to an ordained minister or pastor known as a teaching elder, or a minister of the word and sacrament.