IHS: In Greek, the first three letters of the name of Jesus.

Immaculate Conception: Catholic dogma concerning Mary and the name of a feast in her honor celebrated Dec. 8. It refers to the Catholic belief that Mary was without sin from the moment she was conceived.

Incense: Incense (material used to produce a fragrant odor when burned) is used as a symbol of the Church's offering and prayer going up to God.

Indulgence: The remission before God of the temporal punishment due for sins already forgiven.

Intercessions: A series of prayers for the Church, the world, the Pope, clergy and laity, and the dead.

Intercommunion: The agreement or practice of two Ecclesial communities by which each admits members of the other communion to its sacraments.