The ankh is composed of three elements: a teardrop or oval loop at the top, a vertical stem descending below it, and a horizontal crossbar intersecting the stem. It resembles a cross with a loop in place of the upper vertical arm — and this resemblance is not accidental. The ankh is both cross and loop simultaneously: it combines the linear and the circular, the directed and the encompassing, in a single form that neither element could achieve alone.
The etymology is both simple and profound: ꜥnḫ in ancient Egyptian means "life" — but also "to live," "living," "alive," "mirror" and "bouquet of flowers." The word is the same for the symbol and the concept. In ancient Egyptian thought, the distinction between a word, its written symbol and the reality it refers to was not as sharp as in modern Western thinking: the sign was the thing, in a deep sense. To draw the ankh was to invoke life itself.
The origin of the form has been debated for two centuries without resolution. Proposed explanations include: a stylised sandal strap (the Egyptian word for sandal, ꜥnḫ, is written with the same root); a combination of the male and female genitalia; a stylised uterus and fallopian tubes; a knot or tyet amulet; or simply an abstracted form of the rising sun over the horizon. The most likely explanation may be that the form was felt before it was theorised — that its rightness as a symbol of life was intuited, and the explanations came later.