An apostolnik or epimandylion is an item of clerical clothing

Clerical clothing

Clerical clothing is non-liturgical clothing worn exclusively by clergy. It is distinct from vestments in that it is not reserved specifically for services. Practices vary: clerical clothing is sometimes worn under vestments, and sometimes as the everyday clothing or street wear of a priest,...

 worn by Orthodox Christian

Eastern Orthodox Church

The Orthodox Church, officially called the Orthodox Catholic Church and commonly referred to as the Eastern Orthodox Church, is the second largest Christian denomination in the world, with an estimated 300 million adherents mainly in the countries of Belarus, Bulgaria, Cyprus, Georgia, Greece,...

 and Eastern Catholic nun

Nun

A nun is a woman who has taken vows committing her to live a spiritual life. She may be an ascetic who voluntarily chooses to leave mainstream society and live her life in prayer and contemplation in a monastery or convent...

s. It is a cloth veil

Veil

A veil is an article of clothing, worn almost exclusively by women, that is intended to cover some part of the head or face.One view is that as a religious item, it is intended to show honor to an object or space...

 that completely covers the head (except for the face), neck, and shoulders similar to the hijab

Hijab

The word "hijab" or "'" refers to both the head covering traditionally worn by Muslim women and modest Muslim styles of dress in general....

 worn by Muslim women, it is usually black, but sometimes white. It is sometimes worn with a skufia

Skufia

A skufia is an item of clerical clothing worn by Orthodox Christian and Eastern Catholic monastics or awarded to clergy as a mark of honor...

.

The nun typically receives the apostolnik when she becomes a novice

Novitiate

Novitiate, alt. noviciate, is the period of training and preparation that a novice monastic or member of a religious order undergoes prior to taking vows in order to discern whether they are called to the religious life....

. While it is usually replaced with the epanokamelavkion

Epanokamelavkion

An epanokamelavkion is an item of clerical clothing worn by Orthodox Christian monastics who are rassophor or above, including bishops...

when the nun becomes a rassophor, many nuns will continue to wear the apostolnik for the sake of convenience, much as a monk will continue to wear a skufia instead of a klobuk

Klobuk

thumbA klobuk is an item of clerical clothing worn by Eastern Orthodox and Eastern Catholic monastics and bishops, especially in the Russian tradition...

 when not attending the Divine Liturgy

Divine Liturgy

Divine Liturgy is the common term for the Eucharistic service of the Byzantine tradition of Christian liturgy. As such, it is used in the Eastern Orthodox and Eastern Catholic Churches. Armenian Christians, both of the Armenian Apostolic Church and of the Armenian Catholic Church, use the same term...

.

In some practices, a novice will wear a black scarf covering the head and tied under the chin. She will then receive the apostolnik at her tonsure

Tonsure

Tonsure is the traditional practice of Christian churches of cutting or shaving the hair from the scalp of clerics, monastics, and, in the Eastern Orthodox Church, all baptized members...

. In this practice, the epanokamelavkion may be reserved for the abbess and for nuns of the Great Schema.