Across shaped like a T with a loop at the top, the Egyptianhieroglyph representing the Egyptiantriliteralꜥnḫ(“life”) and often used as anamulet or charm for this concept.
1994, Mira Bartok, Christine Ronan,Ancient Egypt and Nubia,page11:
On temple wall paintings, theankh is often seen being carried by gods who hold it up to the nose of the pharaoh. This gesture symbolizes the offering of the "breath of life" or eternity. Sometimes the pharaoh is also depicted with a stream of water in the form ofankhs being poured over him during a purification ritual.
2001, Anna Franklin, Paul Mason,Lammas: Celebrating Fruits of the First Harvest,page245:
Theankh combines the male and female sexual symbols: a female oval surmounting a male cross. It was also called the Key of the Nile, and was said to represent the sacred marriage between the God and Goddess which took place each year at the source of the Nile before the river flooded. Egyptians regarded theankh as a universal life charm.