Not To Be Confused With
Schism concerns broken COMMUNION; heresy concerns false DOCTRINE. The Great Schism of 1054 divided East and West largely over authority and the Filioque, not over the Trinity itself.
From Greek schisma, “a tear” (the word used for the rip in a garment). A schism is a tearing of the Church's visible unity into separated communions. It may be driven by doctrine, but it is defined by the breach of fellowship, not by heresy as such.
Major examples: the East–West Schism (1054) and the Reformation. The Filioque dispute shows how doctrine and communion intertwine without being identical.