You're thinking of the Eastern Schism, sometimes called the
Great Schism, but in the Catholic Church, the Great Schism refers
to the Western Schism in the 15th century, not the Eastern Schism
in the 11th century.
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The Great Schism was the division of Chalcedonian Christianity
into the Eastern (Greek) and Western (Latin) branches. The Great
Schism began in Constantinople in 1053.