The ankh is the Egyptian symbol of eternal life. The ankh represents the union of man and woman and symbolizes the creation of life through this union. According to one of the theories regarding the origin of the ankh, the symbol might be the combination of the male and female symbols representing Osiris and Isis, the cross and the oval, respectively. It was believed that the union of Osiris and Isis flooded the Nile every year and gave Egypt life by providing fertility. That is why the symbol is also known as “the Key of the Nile” and this is also the reason it is considered to represent the union of heaven and earth.
The horizontal part of the cross represents the division between the heaven and earth while the vertical part is considered to represent the two-way communication between these two realms.