In general, the letters are expressed as the ten divine attributes known as sefirot, the letters being synonymous with them: Ḥokhma, Bina, Tiferet, Malkhut, and their root, Keter. They are ten sefirot because the sefira of Tiferet encompasses six sefirot: Ḥesed, Gevura, Tiferet, Netzaḥ, Hod, and Yesod, and the root is called Keter.7Keter is referred to as the root sefira in this context because Keter is like a bridge, so to speak, between the Creator and the creation.
It is connected to the infinity of the Divine on one side and to the finite creation on the other. Thus it acts as a doorway, a link between His essence and the finite world. Without this doorway, there could be no process of creation at all. Note, however, that it cannot truly be thought of as a “bridge,” since His essence is infinite and can never be reached or grasped by anything within creation. However, they are mainly referenced as Ḥokhma and Bina, Tiferet, and Malkhut. Keep this in mind.