Apostolic
In everyday English, apostolic mostly appears in titles connected with the papacy, or means vaguely missionary. In Orthodox understanding it means deriving from the apostles: the apostolic faith is the faith the apostles received from Christ and handed on, and apostolic succession is the unbroken continuity of that faith, worship and ordination from the apostles to today's bishops. The Church is apostolic because she keeps that faith and is sent, as they were, to preach it.