Names of God (Judaism)

In the Judaic tradition, God's name may not be pronounced. It is most holy, the name that created the universe. Even representations of God's name are holy, the most holy being the tetragrammaton Y (yod), H (he), V (vav), H (he) - "I am that I am" - which was only pronounced once a year, by the high priest at the Feast of Atonement. Many other names or arrangements of letters also describe God in one aspect or reflect such names and are the bases of mystic rituals and esoteric practices.