Their members are called Eastern Orthodox , although there is another group of Churches called Oriental Orthodox that is not Eastern Orthodox . Thus it is that many Orthodox Churches adopt a national title ( e.g. Albanian Orthodox , Bulgarian Orthodox , Georgian Orthodox , Greek Orthodox , Russian Orthodox , Macedonian Orthodox , Romanian Orthodox , Serbian Orthodox , Ukrainian Orthodox etc. ) and this title serves to distinguish which language , which bishops , and which of the typica is followed by that particular congregation . In the Middle East , Orthodox Christians have also been often referred as Roman ( or Rum ) Orthodox , because of their historical connection with the Eastern Roman ( Byzantine ) Empire .