A catechumen (Greek: κατηχούμενος) is one who is preparing for baptism in the Church. In modern usage, catechumen can also refer to one who is preparing for chrismation (or another form of reception) to be received from a heterodox Christian communion.
In the ancient Church, the catechumenate, or time during which one is a catechumen, often lasted for as much as three years and included not only participation in the divine services but also catechesis, formal instruction from a teacher, often the bishop or appointed catechist. Exorcists often performed the catechetical role, as well, following their initial prayers of exorcism over the one being made a catechumen, which is the traditional manner of receiving a catechumen into the community of the Church.
Catechumens are understood to be Christians upon beginning their catechumenate, and should they die before baptism, they are traditionally given an Orthodox funeral.
As the Church eventually became the majority religion of the lands in which it sojourned, the catechumenate as an institution gradually died out in many places, as most Christians were being baptized shortly after birth. As Orthodoxy has moved into the West and Far East and begun gaining converts to the faith, the catechumenate has been significantly rejuvenated.
Catechetical instruction in Orthodoxy in America does not typically last the three years which was common in the time of St. John Chrysostom, but typically can last from six months to a year, depending on the practice of the bishop, his jurisdiction, and the level of spiritual maturity of the catechumen. Local parish priests typically oversee the catechesis of those preparing to be received into the Church.
The Orthodox Church has no formal catechism, a single body of work that details the specifics of its faith. This is one difference between the Orthodox Church and the Roman Catholic Church, who does have a specific catechism.
[from OrthodoxWiki, http://orthodoxwiki.org/Catechumen]
My family and I are catechumens in the Church. We were to begin our instruction with Fr. Anthony's Basic Class on Orthodoxy, but due to a misprint in the bulletin the class was not offered the night we were in attendance. Rather it was the night during Holy Lent when the entire Canon of St. Andrew of Crete was prayed with the Little Compline.
One might call this a pretty big mistake. The Canon is very long and thorough, and very different than a class session, in the traditional sense. However, it was fitting that this "mistake" happened to us. Catechesis is very important - and by catechesis I mean here formal instruction via books or a catechist. But in Holy Orthodoxy the Liturgy and the prayer canons and offices are in themselves a catechist.
If a person only read of Orthodoxy and talked about Orthodoxy, and learned from there to think in an Orthodox way, and to speak like the Orthodox speak, and to love the things the Orthodox like, this would in no way make such a person an Orthodox Christian. Rather, to be Orthodox means to be Orthodox. A person is Orthodox who first has finally chosen to be Orthodox and has been received by the Church (like a mother receiving her adopted and beloved child). And from there one begins to be Orthodox by daily seeking to become Orthodox, by soaking up Orthodoxy and engaging in Orthodoxy through the life of repentance, prayer, worship, and merciful action in the world.
So as catechumens, that is, as a learner and an infant in the new creation of Christ's kingdom that is Holy Orthodoxy, we began in one of the best ways possible. We began to learn the cry of repentance. Were we surprised? Yes. By the change in plans? At first, but then by how much our souls needed this sort of prayer. And then after that, how rich and full of the Scriptures this prayer is - both in content and in spirit. Next to our weekly attendance at the Divine Liturgy, the Canon of St. Andrew of Crete was the best way to begin our life as catechumens in Holy Orthodoxy.
Below is an excerpt. The full text, broken up over four nights, is available from Monochos.net. A synopsis of the canon's author, St. Andrew of Crete, is located at Wikipedia.
Stasis One, Ode 5
Eirmos: Out of the night watching early for Thee, enlighten me, I pray, O Lover of men, and guide even me in Thy commandments, and teach me, O Saviour, to do Thy will.
Refrain: Have mercy on me, O God, have mercy on me.
I have passed my life ever in night, for the night of sin has been to me thick fog and darkness; but make me, O Saviour, a son of the day. (Ephesians 5:8)
Like Reuben, wretch that I am, I have planned an unprincipled and lawless act against God Most High, having defiled my bed as he defiled that of his father. Genesis 35:21; 49:3-4)
I confess to Thee, O Christ my King: I have sinned, I have sinned, like Joseph's brothers of old, who sold the fruit of purity and chastity. (Genesis 37)
Righteous Joseph was given up by his brothers, that sweet soul was sold into slavery, as a type of the Lord; and you, my soul, have sold yourself completely to your vices. (Genesis 37:27-28)
Imitate, wretched and worthless soul, righteous Joseph and his pure mind, and do not be wanton with irrational desires, ever transgressing. (Genesis 39:7-23)
If Joseph of old also occupied a pit, O Sovereign Lord, yet it was as a type of Thy Burial and Rising. But will I ever offer Thee anything like it? (Genesis 37)
Glory to the Father, and to the Son, and to the Holy Spirit:
To the Holy Trinity: Thee, O Trinity, we glorify, the one God: Holy, Holy, Holy art Thou, Father, Son and Spirit, simple Being, Unity ever adored.
Now and ever, and to the ages of ages. Amen.
Theotokion: From thee, O pure maiden Mother and Virgin, God Who created the worlds and ages was clad in my clay and united to Himself human nature.
The Eirmos is repeated, ...