The Hebrew term for letter transformations is chilufei otiyot , which literally means “the interchanging of letters. There are a number of different transformation schemes used in Kabbalah, but in principle any of the possible pairings of the 22 letters constitutes a valid transformation and is referred to as an alef-beit.
In Sefer Yetzirah, 22 such alef-beits are described (as the logically ordered basis of all the two-letter subroots of the Hebrew language; [Rela she’arim]). See also our article, Hebrew: The Ideal Programming Language.
The six most common transformation systems are: