Clergy are some of the formal leaders within certain religions. The roles and functions of clergy vary in different religious traditions but these usually involve presiding over specific rituals and teaching their religion's doctrines and practices. Some of the terms used for individual clergy are cleric, clergyman, clergywoman, clergyperson, and churchman.In Christianity the specific names and roles of clergy vary by denomination and there is a wide range of formal and informal clergy positions, including deacons, priests, bishops, preachers, pastors, and ministers. In Islam, a religious leader is often known formally or informally as an imam, mufti or ayatollah. In Jewish tradition, a religious leader is often a rabbi or hazzan (cantor).