Cross, cultural symbol, often consisting of an upright and a crosspiece. The cross appeared in cultures of Egypt, ancient India, and North America. Used by ancient Romans for execution by crucifixion, it became the principal symbol of the Christian religion. There are 4 basic forms of the Christian cross: the Latin cross, the most common, in which the upright is longer than the transom that crosses it near the top; the Greek cross, an upright crossed at right angles at its center by a beam of the same length; the tau, or St. Anthony's cross, in the form of a T; and St. Andrew's cross in the form of an X. The other forms, such as the papal cross, an upright crossed by 3 bars, are mainly inventions for ecclesiastical or hierarchical purposes.