Concelebration is the act of multiple clergy conducting divine services together. Rubrics dictate what changes are made in the services when a concelebration occurs, as distinct from when the services are performed by only one priest or also a deacon. Concelebration is often a sign of full fellowship and communion between jurisdictions which recognize each other as fully Orthodox. Hierarchical services are a special type of concelebration including one or more bishops, significantly altering the text and movement in a service.