Christianity has not generally practised aniconism, or the avoidance or prohibition of types of images, even if the early Jewish Christians sects, as well as some modern denominations, preferred to some extent not to use figures in their symbols, by invoking the Decalogue's prohibition of idolatry. The cross, which is today one of the most widely recognised symbols in the world, was used as a Christian symbol from the earliest times. Tertullian, in his book De Corona, tells how it was already a tradition for Christians to trace repeatedly on their foreheads the sign of the cross.Although the cross was known to the early Christians, the crucifix did not appear in use until the 5th century.
Among the symbols employed by the primitive Christians, that of the fish or Ichthys seems to have ranked first in importance. From monumental sources such as tombs it is known that the symbolic fish was familiar to Christians from the earliest times. The fish was depicted as a Christian symbol in the first decades of the 2nd century.Its popularity among Christians was due principally, it would seem, to the famous acrostic consisting of the initial letters of five Greek words forming the word for fish (Ichthys), which words briefly but clearly described the character of Christ and the claim to worship of believers: Iesous Christos Theou Yios Soter (Ίησοῦς Χριστός, Θεοῦ Υἱός, Σωτήρ), meaning, Jesus Christ, Son of God, Saviour.
Other major Christian symbols include the chi-rho monogram, the dove (symbolic of the Holy Spirit), the sacrificial lamb (symbolic of Christ's sacrifice), the vine (symbolising the necessary connectedness of the Christian with Christ) and many others. These all derive from writings found in the New Testament.