Bulgarian issue
The Bulgarian struggle for ecclesiastical autonomy. Since the 1850’s the Bulgarians claimed the establishment of an autonomous church (exarchate) which would retain typical relationship with the Ecumenical Patriarchate. The latter opposed to this movement as its role had been undermined. After long lasting negotiations and the failure of any attempt for reconciliation, an Ottoman firman promulgated in 1870 established the Bulgarian exarchate, although the Patriarchate declared the Exarchate schismatic. Naturally, the main character of the struggle of the Bulgarians for ecclesiastical independence was not religious. It was bounded to the Bulgarian nationalism emerged at that time and had clear political dimension (Bulgarian political independence).

Council of Ferrara-Florence (1438)
Ecclesiastical Council assembled at both Italians cities Ferrara and Florence in 1438-1439 and decided the reunion of the Orthodox and Catholic Church. The Ecumenical Patriarchate didn't really accept the decisions of the Council and didn't never practise the reunion.

exarch
At the Byzantine ecclesiastical administration the exarch, from the 5th century onwards, was the head of an ecclesiastical province and later became another title of the Ecumenical Patriarch, certifying that he was the head prelate within the jurisdiction of the Ecumenical Patriarchate. The office of exarch was abolished during the 6th century, although exarchs were metropolites or representatives of metropolites who supervised the ecclesiastical provinces or the ecclesiastical and monastic foundations. During the late 14th century as exarchs are referred the metropolites who were located at ancient dioceses and supervised all the ecclesiastical sees and the charitable institutions of the ecclesiastical province and later the authorized representatives of the Patriarch (patriarchal exarchs).