Catechumen and catechesis
A person preparing for baptism, and the structured instruction they undergo.
A catechumen is a person preparing for baptism, or in the case of an adult convert to Catholic or Orthodox tradition, for full reception into the church through baptism, confirmation or chrismation, and first Eucharist. Catechesis is the period of structured instruction in the faith that the catechumen undergoes: typically a year or more in the Catholic OCIA (Order of Christian Initiation of Adults) programme; in Orthodox tradition the length varies by jurisdiction and parish. The term comes from the Greek katechein, to instruct by word of mouth, and reflects the early Church's practice of preparing adult converts before baptism at the Easter Vigil.