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The Catechism Lesson (1890), by Jules-Alexis Meunier
Wikimedia Commons

A catechumen, from the Greek κατηχούμενοι, meaning “instructed ones”, is a person undergoing instruction in preparation for their baptism into the Christian church. In the early Church, catechumens were either assigned a special place during services or obliged to watch from the narthex,Vestibule before the main entrance to a Christian church, less sacred than the church proper. but were dismissed before the eucharist proper began.[1] The first part of the eucharist, which the catechumens were allowed to witness, has therefore been dubbed the Mass of the Catechumens, or the ante-communion.[2]