"Rabbi"

Dear Rabbi, What are the criteria required to assume the title ‘Rabbi’ in an orthodox community ? How do we know someone is entitled to call himself Rabbi ? Is a certificate of smicha required ? If a congregation appoints a person as their spiritual leader, can he call himself Rabbi ?

A person is authorized to be a Rav if he received authorization from another who had it before him who decided that he has the qualities and the knowledge to receive such authorization. This authorization is given in writing so as to bear testimony to the authorization (R’ma Yoreh Deah 242 14; Aruch HaShulchan Yoreh Deah 242, 28- 29).A person having rabbinic authorization becomes the rabbi of a community when appointed to the position by the community- either officially or by clear implication (Shu"t Iggrot Moshe).