Title: Crucifix
Content:   A crucifix (from Latin cruci fixus meaning "(one) fixed to a cross") is an image of Jesus on the cross, as distinct from a bare cross. The representation of Jesus himself on the cross is referred to in English as the corpus (Latin for "body"). The crucifix is a principal symbol for many groups of Christians, and one of the most common forms of the Crucifixion in the arts. It is especially important in the Latin Rite of the Roman Catholic Church, but is also used in the Eastern Orthodox Church, most Oriental Orthodox Churches (except the Armenian & Syriac Church), and the Eastern Catholic Churches, as well as by the Lutheran, 
Title: Crucifix
Content:  by Saint Paul in Scripture, "we preach Christ crucified, a stumbling block to Jews and folly to Gentiles, but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God". In the West altar crosses and processional crosses began to be crucifixes in the 11th century, which became general around the 14th century, as they became cheaper. The Roman Rite requires that "either on the altar or near it, there is to be a cross, with the figure of Christ crucified upon it, a cross clearly visible to the assembled people. It is desirable that such a cross should remain near the altar even outside 
Title: Christianization
Content:   The cross is currently the most common symbol of Christianity, and has been for many centuries, coming to prominence during the 4th century (301 to 400 AD) And its known to be the most familiar and widely recognized symbol of Christianity today. The predecessor of the cross as the main Christian symbol was the labarum, a symbol formed by overlaying the first two letters of the Greek word for Christ in the Greek alphabet. Constantine I is widely considered to have introduced the symbol into Christianity, but the symbol itself predates this. Although Christian tradition argues that Constantine chose the labarum 
Title: Christian cross
Content:  name ΙΗΣΟΥΣ, standing for 18). His contemporary Tertullian rejected the accusation of Christians being "adorers of the gibbet" (crucis religiosi). In his book De Corona, written in 204, Tertullian tells how it was already a tradition for Christians to trace repeatedly on their foreheads the sign of the cross. The crucifix, a cross upon which an image of Christ is present, is not known to have been used until the 6th century AD. The oldest extant depiction of the execution of Jesus in any medium seems to be the second-century or early third-century relief on a jasper gemstone meant for use as an amulet, which is now in the British Museum in 
Title: Poor Man's Bible
Content:  The Crucifix is in general the most significant single narrative object in the decorative scheme of any church. During the medieval period the crucifix, called the Rood in England, from the Old Saxon roda, was a large crucifix placed conspicuously, often suspended in the Quire or standing on a screen separating either the Quire or the sanctuary from the rest of the church. The suspended crucifix could either be painted or carved of wood. In England where rood screens have often survived without the rood itself, it was general for the crucifix to have accompanying figures of Mary the Mother of Christ and either John the Evangelist or John the Baptist carrying a banner bearing the inscription "Behold, the Lamb of God". In Italy, roods were created by some of the most famous painters and sculptors, such as Giotto, Brunelleschi and Donatello. In many Protestant churches the crucifix has been replaced by a simple cross without a figure, symbolically representing both the redeeming sacrifice and the resurrection to new life offered by Jesus.
Title: Instrument of Jesus' crucifixion
Content: The cross as a Christian symbol or "seal" came into use at least as early as the 2nd century (see "Apost. Const." iii. 17; Epistle of Barnabas, xi.-xii.; Justin, "Apologia," i. 55-60; "Dial. cum Tryph." 85-97); and the marking of a cross upon the forehead and the chest was regarded as a talisman against the powers of demons (Tertullian, "De Corona," iii.; Cyprian, "Testimonies," xi. 21-22; Lactantius, "Divinæ Institutiones," iv. 27, and elsewhere). Accordingly, the Christian Fathers had to defend themselves, as early as the 2nd century, against the charge of being worshipers of the cross, as may be learned from Tertullian, "Apologia," xii., xvii., and Minucius 
Title: Christian symbolism
Content:  a symbol by early Christians, the crucifix, i.e. depictions of the crucifixion scene, were rare prior to the 5th century; some  engraved gems thought to be 2nd or 3rd century have survived, but the subject does not appear in the art of the Catacombs of Rome. The purported discovery of the True Cross by Constantine's mother, Helena, and the development of Golgotha as a site for pilgrimage led to a change of attitude. It was probably in Palestine that the image developed, and many of the earliest depictions are on the Monza ampullae, small metal flasks for holy oil, that were pilgrim's souvenirs from 
Title: Christian cross
Content:  Although Christians accepted that the cross was the gallows on which Jesus died, they had already begun in the 2nd century to use it as a Christian symbol. During the first three centuries of the Christian era the cross was "a symbol of minor importance" when compared to the prominence given to it later, but by the second century it was closely associated with Christians, to the point where Christians were mocked as "adorers of the gibbet" (crucis religiosi), an accusation countered by Tertullian. and it was already a tradition for Christians to trace repeatedly on their foreheads the sign of the cross. Martin Luther at the 
Title: Christianity
Content:  Christianity has not generally practiced aniconism, the avoidance or prohibition of devotional images, even if early Jewish Christians and some modern denominations, invoking the Decalogue's prohibition of idolatry, avoided figures in their symbols. The cross, today one of the most widely recognized symbols, was used by Christians from the earliest times. Tertullian, in his book De Corona, tells how it was already a tradition for Christians to trace the sign of the cross on their foreheads. Although the cross was known to the early Christians, the crucifix did not appear in use until the 5th century. Among the earliest Christian symbols, that of the fish or 
Title: Crucifixion of Jesus
Content:   Since the crucifixion of Jesus, the cross has become a key element of Christian symbolism, and the crucifixion scene has been a key element of Christian art, giving rise to specific artistic themes such as Ecce Homo, The Raising of the Cross, Descent from the Cross and Entombment of Christ. The Crucifixion, seen from the Cross by Tissot presented a novel approach at the end of the 19th century, in which the crucifixion scene was portrayed from the perspective of Jesus. The symbolism of the cross which is today one of the most widely recognized Christian symbols was used from the 

Question: when did the crucifix become the symbol of christianity?
Answer: in the 2nd century.
4th century.
the 4th century.