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Immaculate Conception — the dogma that Mary was conceived without original sin (not to be confused with the Incarnation of Christ)

Incardination — see also: excardination

Incarnation — The Word of God taking on a human nature and becoming true man, Jesus Christ (not to be confused with the Immaculate Conception of Mary)

Institute of consecrated life

Institute, Religious — see: Religious institute

Institute, Secular — see: Secular institute