Qabala

(also Cabala, Kaballah, Cabbala, and many other spellings; the original and "proper" spelling is in Hebrew: qoph beth lamedh (קבל), but that's hard to typeset in Roman)
An ancient Hebrew system of mysticism, based around the Tree of Life and various ways of finding (or creating) correspondences between various otherwise disparate objects, entities, concepts, or symbols. (Gematria is foremost among these.)

The origins of Qabala are lost to misty prehistory; it has been practiced (in varying forms) by Jewish mystics of all known ages. As befitting a system devised by the first People of the Book, it is strongly linear, and relies heavily on linguistic and mathematical correlations. The Tree of Life essentially divides all creation into ten spheres (or sephiroth, singular: sephira), to which all things can be related. Later revisions of the Tree add 22 “paths” connecting the sephiroth in certain combinations related to the 22 letters of the Hebrew alphabet.

Qabala has been adopted by ceremonial magick, to the point that the system is mostly based on Qabala. In the process, nearly everything has been somehow related to the Tree of Life by ceremonial magicians somewhere, with varying degrees of applicability. For example, the 22 trumps of the tarot relate fairly well to the 22 paths. The 24 runes of the futhark, however, or the 64 trigrams of the I Ching, don’t connect so well.