What is an o nk/ankh?

• the Ankh, symbol of life, thoracic vertebra of a bull (seen in cross section)

• the Died, symbol of stability, base on sacrum of a bull's spine

• the Was, symbol of power and dominion, a staff featuring the head and tail of the god   Set, "great of strength"

Egyptian academics, in particular those at the University of Cairo, aver that the ankh has been over-interpreted and that it is representative of the pivotal role of the Nile in the country[citation needed]. The oval head is said to represent the Nile delta, with the vertical mark representing the path of the river and the East and West arms representing the two sides of the country and their unification[citation needed].

It's actually spelled Ankh. It's also known as the Ansata Cross and the Egyptian Cross.

The Ankh Cross is a looped Tau Cross and an old Egyptian hieroglyph meaning life. It sometimes goes by the exotic name Key of the Nile. 

There are several theories about the origin of this design. One suggestion is that the symbol looks like the posts that aligned the banks of the Nile River to indicate the high-water mark of floods. Since the floods bring new and fertile soil, this became the symbol of renewed life. 

Another theory to connect this hieroglyph to life, is from the symbolic representation of a sandal's thong with a loop going around the ankle. In ancient Egyptian, sandal thong and life had the same pronunciation (homophony). Deciding on a hieroglyph for sandal thong was relatively easy; they simply drew what they saw. But deciding on something for the less tangible life, was a challenge. So they used the hieroglyph that had the same sound.

This occurs frequently in non-phonetic languages and is known as the Rebus Principle. (The English word ankle is derived from Indo-European ank.)

Ankh symbol, seen in the centre of this ancient Egyptian relief And yet another theory goes that the Ankh symbol is a sketch of the womb, in addition to being a sketch of the sexual union of male and female genitalia. By extension, we imagine zest, energy, reproduction, regeneration, and immortality. 

For many civilizations using this symbol, the loop represented the sun and it was held by many gods including Atum, the sun-god of Heliopolis. The loop is also a perfect symbol that has neither beginning nor end, so it represents the eternal soul. 

The entire symbol is also a key, to unlock hidden mysteries in the Kingdom of the Dead and was often used in funeral rites. The symbol also represents the Tree of Life, with its trunk and foliage.

An Osiris Pillar of Senusret I from the 12th Dynasty.