ex-2 Also ec-.
[>Greek ex, out of.]
This prefix is closely related to its Latin equivalent (see the previous entry) but is much rarer. Examples are exarch (Greek exarkhos, from arkhos, ruler), a bishop of the Orthodox Church, exodus (Greek exodos, from hodos, way), and exorcize (ecclesiastical Latin exorcizare, from Greek exorkizein, from horkos, oath).
Before consonants it was replaced in Greek by ek-, which has become ec- in English, for example in eccentric (Greek kentron, centre), eclipse (Greek ekleipein, fail to appear, be eclipsed, from leipein, to leave), ecstasy (Greek ekstasis, standing outside oneself, based on histanai, to place), and eczema (Greek ekzein, boil over, break out, from zein, boil).
A few specialist modern formations exist, such as exergonic (Greek ergon, work), a biochemical reaction that proceeds with release of energy, and exstrophy (Greek strophē, turning), a birth defect resulting in the turning inside-out of a hollow organ, but the prefix is hardly productive.
Words such as exotic contain exo- instead.